CN1311618C

CN1311618C - Switching power source device

Info

Publication number: CN1311618C
Application number: CNB031577652A
Authority: CN
Inventors: 北野三郎
Original assignee: Sharp Corp
Current assignee: Sharp Corp
Priority date: 2002-08-28
Filing date: 2003-08-28
Publication date: 2007-04-18
Anticipated expiration: 2023-08-28
Also published as: JP2004088959A; US6903945B2; US20040042239A1; CN1489270A

Abstract

A switching power supply apparatus operates with less power consumption as a whole as a result of reduced power loss suffered while the switching operation of the main switching device is being stopped in burst switching control. Burst switching control is achieved by a signal level checker circuit 15 repeatedly turning on and off a switch circuit 17 provided in the line by way of which a switching controller circuit 19 is supplied with operating power. In burst switching control, when the switching operation of a main switching device 5 is being stopped, the supply of operating power to the switching controller circuit 19 is also stopped. This helps reduce the power loss suffered while the switching operation is being stopped, and thus helps reduce the power consumption of the apparatus as a whole.

Description

Switching power unit

Technical field

The present invention relates to switching power unit, it can be used as DC power supply and uses in electronic equipment.

Background technology

For example, intend having disclosed among the open No.H10-304658 the well-known example of this class switching power unit at Japanese patent application.Have at the switching power unit disclosed in this patent: conducting and by the main switch of direct current that is applied to transformer; The conduction and cut-off signal of being responded in rectification and the level and smooth transformer secondary output coil is so that the secondary side rectification/smoothing circuit that provides as main output signal; The accessory power supply that rectification and the conduction and cut-off signal of smoothly being responded in the bias coil of transformer provide as accessory power supply voltage; Generation is illustrated in the error amplifier of the error voltage signal of difference between the accessory power supply voltage of accessory power supply voltage output and the reference voltage, and the conduction and cut-off control signal is inputed to the comparator that main switch reduces the error voltage signal that error amplifier exports by this way.This switching power unit also comprises underload switch controller part, it can main output voltage become the conduction and cut-off that temporarily stops main switch when being higher than upper voltage limit operation and main output voltage become the conducting of restarting main switch when being lower than lower voltage limit/by operation.

In this conventional switching power unit, the operation of being carried out makes and to become the main output voltage when the rectification on secondary one side/smoothing circuit output the conduction and cut-off operation of main switch just stops when being higher than upper voltage limit temporarily, and operates and just restart when the main output voltage conduction and cut-off of main switch that becomes when being lower than lower voltage limit.

But, here, when main output voltage becomes the conducting that just temporarily stops main switch when being higher than upper voltage limit/by operation, keep operating voltage to offer driving and the control circuit of control main switch in each circuit and control device.This will produce bigger power loss.Particularly, in the become conduction and cut-off operation that just stops main switch when being higher than upper voltage limit and in main output voltage becomes the structure that the conduction and cut-off that just restarts main switch when being lower than lower voltage limit operates of the principal voltage when the rectification on secondary one side/smoothing circuit output temporarily, promptly, in so-called pulse strobe switch control, even stopped switching manipulation, but all circuit and the control device that still continue in control circuit to be had provide power supply.This will the electric consumption electric current, thereby produces the waste of power loss.

Intend also having disclosed the ordinary tap supply unit among open No.2001-346378 and the No.2002-58238 at Japanese patent application, it is similar to the above-mentioned switching power unit of discussing, even in the cycle that the switching manipulation of main switch stops with the gating switch control mode, all circuit and the control device that still continue in the switching signal control circuit provide working power.This will cause the waste loss of source current.

By the way, intend in order to reduce the power loss in holding state, in this state, stopping the switching manipulation of main switching device in the ordinary tap supply unit disclosed in the open No.2001-86745 at Japanese patent application.So purpose of the present invention is not to reduce the power consumption of being born when the switching manipulation of main switching device stops in the pulse gate mode.

Summary of the invention

An object of the present invention is to provide switching power unit, by the power consumption that reduces to be born when the switching manipulation of main switching device stops in the pulse gate mode, this device can be on the whole with less power loss work.

In order to achieve the above object, according to an aspect of the present invention, switching power unit has the series circuit that comprises transformer and main switching device, and this series circuit is connected between the positive and negative power line, and the positive and negative power line is connecting DC power supply.The direct voltage that switching power unit output obtains by rectification, this direct voltage are to obtain by the rectifier of main switching device being carried out the high frequency voltage that switching manipulation responds at the secondary coil of transformer.Here, switching power unit uses feedback signal as the comparative result between direct voltage and preset reference voltage, and by conducting with end and drive main switching device, according to the signal level of feedback signal, provide working power to the main switching device drive system that drives main switching device.

In this switching power unit according to the present invention, for example, in heavy duty operation, can reduce output voltage.In order to correct this situation, just produced more low level feedback signal.This requires to continue to provide working power to the main switching device drive system, so main switching device can continue switching manipulation.On the other hand, in light load operation,, will produce the feedback signal of higher level when output voltage becomes when being higher than predetermined value.This will cause that the working power that offers the switching device drive system stops, so main switching device will the shutdown switch operation.Therefore, output voltage just turns back to predetermined numerical value.

Promptly, employing is according to this switching power unit of the present invention, when the switching manipulation of main switching device stops with the pulse strobe switch control mode, the working power that offers the main switching device drive system also stops, this helps to reduce the electrical source consumption that born when shutdown switch is operated, so this helps to reduce the loss of power of device integral body.

According to a further aspect in the invention, switching power unit has the series circuit that comprises transformer and main switching device, and this series circuit is connected between the positive and negative power line, and the positive and negative power line is connecting DC power supply.The direct voltage that switching power unit output obtains by rectification, this direct voltage are to obtain by the rectifier of main switching device being carried out the high frequency voltage that switching manipulation responds at the secondary coil of transformer.Here, switching power unit further comprises: output voltage detector, the direct voltage that this detector obtains preset reference voltage and rectifier are compared and are exported comparative result as feedback signal; On-off controller, this controller are used for driving and control main switching device according to the feedback signal that output voltage detector is exported; The signal level verifier, it is used to monitor the signal level of feedback signal and the operating control signal that output is used for coming according to the supervisory signal level opening and closing on-off controller; And operation/not operation derailing switch, it provides in online mode, can provide working power and according to the operating control signal opening and closing on-off controller from the signal level checker to on-off controller by it.

In this switching power unit according to the present invention, in underloaded operation, when output voltage trends towards increasing, promptly, when output voltage is higher than predetermined numerical value, then the signal level of the feedback signal of output voltage detector output for example is high, and the signal level checker is with the operating control signal feed-in operation/not operation derailing switch of request not operation, and operation/not operation derailing switch stops to offer the working power of on-off controller subsequently.

Therefore, the operation of main switching device shutdown switch is so out-put supply begins progressively to descend.The signal level of the feedback signal of exporting when output voltage detector is step-down for example, then the signal level verifier is just with the operating control signal feed-in operation/not operation derailing switch of solicit operation, so operation/not operation derailing switch begins to provide working power to on-off controller.

Therefore, main switching device just restarts switching manipulation, so output voltage just begins progressively to increase.When the signal level of feedback signal became high once more, then the signal level checker was just to ask the operating control signal feed-in operation/not operation derailing switch of not operation, so operation/not operation derailing switch just stops to provide working power to on-off controller.Therefore, main switching device is operated with regard to shutdown switch, so output voltage just begins progressively to descend.When repeating this sequence of operation, output voltage just remains on the predetermined numerical value.

In this switching power unit, when output voltage trends towards descending, promptly, when output voltage is lower than predetermined value, then the signal level of the feedback signal exported of output voltage detector is for example for low, the signal level checker just with the operating control signal feed-in operation/not operation derailing switch of solicit operation, so operation/not operation derailing switch provides working power with regard to continuing to on-off controller, thereby continues to carry out switching manipulation.

Employing is according to switching power unit of the present invention, the pulse strobe switch control that is obtained is the result that the signal level checker repeats opening and closing operation/not operation derailing switch, and this operation/not operation derailing switch provides working power in online mode to on-off controller.In addition, when stopping the switching manipulation of main switching device, also stopped the working power that provides to on-off controller in the pulse strobe switch mode.This helps to reduce the electrical source consumption that born when shutdown switch is operated, so help to reduce the power loss of device integral body.

Preferably, the feedback signal that output voltage detector is exported is that the photoelectric tube by photoelectrical coupler transfers to on-off controller, and the signal level checker is by the relatively current level of photoelectrical coupler phototransistor and the signal level that reference current levels monitors feedback signal.

Adopt this structure, just can be according to the mode of operation of the comparative result control impuls gating between current values that flows through phototransistor and the reference current numerical value.The load current value of the signal level of feedback signal (that is, flowing through the current values of phototransistor) expression switching power unit.So, just load current value correctly might be provided with to carry out switch motion between the operation of switching manipulation and pulse strobe switch continuously on this value.

In the pulse switch operation, output voltage fluctuates.Yet, because the signal level of feedback signal is represented the output voltage several value, so the upper and lower bound numerical value of output voltage just might correctly be set.

Preferably, the phototransistor of current sensing resistor and photoelectrical coupler is in series, and the signal level checker comes opening and closing by the method for operating control signal input switch controller, wherein, operating control signal is to check the comparison of the voltage of reference power source to obtain by voltage drop on the current sensing resistor and current level.

Adopt this structure, just might make the signal level checker can detect the signal level of feedback signal according to the voltage drop on the current sensing resistor, comparison signal level and current level check reference voltage, and the working power that offers on-off controller according to these comparative result opening and closing.

Preferably, the working power of on-off controller provides by the starting current power line, this starting current is provided by startup resistor by positive power line, perhaps as stable operating current power supply, and the working power of signal level checker can be provided by the auxiliary control source that node extracted between a plurality of diodes the voltage of being responded to by the transformer secondary output coil after the rectification of the series circuit that a plurality of diode is formed.

Adopt this structure, when switching power unit begins to start, under the effect of diode, might avoid supposing that electric current flow into the steady operation current power supply line from the starting current power line.This helps to reduce to start the required time, also helps to reduce the resistance value of startup resistor, thereby reduces power consumption.

In other words, provide the switching power unit of working power to compare with the on-off controller that does not have control impuls gating switch function and operate to the execution pulse strobe switch in this control impuls gating switch mode, when switching power unit begins to start, switching power unit of the present invention can start the short time, can reduce the unwanted power consumption that startup resistor consumes simultaneously.

Preferably, auxiliary control source provides the working power of the phototransistor of signal level checker and photoelectrical coupler, and wherein auxiliary control source is that node extracts and provide institute's induced voltage in the transformer secondary output coil that adopts after a plurality of diode rectifications between a plurality of diodes from the series circuit that constitutes the steady operation current and power supply.

Adopt this structure, when switching power unit began to start, diode avoided starting current to flow into auxiliary control source.This just helps to shorten start-up time.In addition, in steady operation, make to be fed into the phototransistor of signal level checker and photoelectrical coupler by the rectification direct voltage that induced voltage obtained in the transformer secondary output coil as working power.This has guaranteed steady operation.

Preferably, on-off controller is realized with control circuit for pulse-width modulation, control circuit for pulse-width modulation output drives the pulse signal as the main switching device drive signal, and this pulse signal is the pulse width modulating signal of the voltage level of the feedback signal exported according to output voltage detector.

Adopt this structure, the drive signal that adapts fully with the voltage level with feedback signal drives main switching device.This helps to improve the stability of switching power unit output voltage.

Preferably, the control circuit for pulse-width modulation that uses can be the pulse width modulation controlled integrated circuit (for example, the production number of Fuji Electronics Co., Ltd. manufacturing is the integrated circuit of FA 5511), it is to adopt the mode of integrated circuit (IC) chip to realize and feedback end points and an input of having input voltage relevant with feedback signal at least is applicable to the soft start capacitor end points that enables or forbid the voltage of internal circuit.

Adopt this structure, might reduce to drive the shared space of circuit of main switching device, and can improve the stability of output voltage, thereby make equipment miniaturization.

Preferably, when the pulse width modulation controlled integrated circuit is used for on-off controller, also provide: end the startup adjuster that the pulse width modulation controlled integrated circuit starts with the school; Be connected the feedback end points of pulse width modulation controlled integrated circuit and first resistor between the negative power line; The signal level checker is according to the check results of the signal level of feedback signal, with operating control signal and inverted feedback signal respectively feed-in can be used as soft start capacitor endpoint controller and the feedback end points that operation/not operation derailing switch uses; The soft start capacitor endpoint controller is connected the soft start capacitor end points of pulse width modulation controlled integrated circuit according to operating control signal and disconnects with negative power line; And start adjuster and will feed back end points according to the voltage level of auxiliary control source by second resistor and be connected with negative power line and disconnect.

Adopt this structure, when switching power unit starts, when the voltage of auxiliary control source increases, instantaneous before electric current begins to flow through phototransistor, the startup adjuster is in parallel second resistor and is connected with first resistor, thereby and reduces at the resistance that feeds back between end points and the negative power line.This just makes and reduces at the potential voltage that feeds back end points.Like this, when switching power unit begins to start, just can keep best level, to allow the reliable rising of output voltage at the voltage that feeds back end points.In addition, in stable state, switching power unit allows the reliable burning voltage of output.

Preferably, the signal level checker comprises pair of transistor, and their emitter is joined together to form comparator; And a base stage in the transistor is connecting the node between current sensing resistor and the phototransistor, and transistorized another base stage is connecting the reference power source of current level detector; A transistorized collector electrode is connecting the feedback end points of pulse width modulation controlled integrated circuit, and transistorized another collector electrode is connecting the soft start capacitor endpoint controller.

Adopt this structure, just might easily realize being applicable to the signal level of feedback signal and the current level comparator relatively of current level verification reference power source.

Preferably, the soft start capacitor endpoint controller comprises a NPN transistor, this transistorized collector electrode is connected with the soft start capacitor end points of pulse width modulation controlled integrated circuit, emitter is connected with negative power line, and another included transistorized collector electrode is connected in base stage and the signal level checker.

Adopt this structure, the soft start capacitor endpoint controller provides the NPN transistor that connects in the above-mentioned mode of being discussed, so, just might adopt simple structure to enable and forbid the pulse width modulation controlled integrated circuit.

Preferably, starting adjuster comprises: the series circuit of being made up of Zener diode and a plurality of resistor that is connected between auxiliary control source and the negative power line; And a NPN transistor, this transistorized base stage is connecting the node between the resistor, and collector electrode is connected with the feedback end points of pulse width modulation controlled integrated circuit by second resistor, and emitter is connected with negative power line.

Adopt this structure, provide the startup adjuster, might adopt simple structure to make switching power unit export reliable and stable voltage in the mode of stable operation with the series circuit and the NPN transistor of above-mentioned discussion.

Preferably, the signal level checker comprises: be applicable to the voltage voltage grading resistor that produces reference voltage, the resistor that the low voltage of this voltage voltage grading resistor is one section can be divided into two resistors, and wherein node between the two is connected with the soft start capacitor end points of pulse width modulation controlled integrated circuit by diode.

Adopt this structure, be used to produce the resistance value of each voltage grading resistor of reference voltage, the fluctuation width and the pulse gate cycle of the output voltage of pulse strobe switch mode of operation work might be set free and exactly by variation.Particularly, make that the fluctuation width of output voltage can be the same with the width of using permission, this just might reduce unwanted power loss in pulse strobe switch.

Preferably, switching power unit also comprises: be connected the soft start capacitor end points of pulse width modulation controlled integrated circuit and the capacitor between the negative power line; And be connected diode between capacitor and the soft start capacitor end points.

Adopt this structure, in the pulse gate operation, might accelerate the fluctuation of voltage level on the soft start capacitor end points, thereby accelerate the switching speed between the state of the state of carrying out switching manipulation and shutdown switch operation by the effect of diode.In addition, in the pulse strobe switch operation, might reduce the fluctuation of output voltage and the accuracy that improves the upper and lower bound of output voltage.In addition, when load current when pulse strobe switch operating period increases suddenly, just might shorten moving to the required time of continuous switching manipulation, thereby and avoid the decline of output voltage.

Preferably, when the pulse width modulation controlled integrated circuit was used for on-off controller, switching power unit also comprised: be connected between the feedback end points of pulse width modulation controlled integrated circuit and the negative power line to adjust the current regulator of feedback end points output current according to the signal level of feedback signal; And according to the output signal of signal level checker be connected with negative power line by soft start capacitor end points the pulse width modulation controlled integrated circuit and the operation that disconnects as the soft start capacitor endpoint controller of operation/not operation derailing switch use.

Adopt this structure, when the startup at switching power unit, current regulator is adjusted to high numerical value with the voltage of the feedback end points of pulse width modulation controlled integrated circuit.So the pulse width modulation controlled integrated circuit makes main switching device carry out switching manipulation with the duty ratio of bigger conducting state, thereby and reduce start-up time.In addition, the soft start capacitor endpoint controller makes the soft start capacitor end points of pulse width modulation controlled integrated circuit be connected with negative power line according to the output signal of signal level checker and disconnects, thus opening and closing pulse width modulation controlled integrated circuit.

Preferably, current regulator comprises a NPN transistor, this transistorized collector electrode is connecting the feedback end points of pulse width modulation controlled integrated circuit, and emitter is connecting negative power line by a resistor, with and base stage connecting the holding wire of feedback signal.

Adopt this structure, current regulator has and starts the more simple structure of adjuster, but can obtain identical effect.That is, might adopt this comparatively simple structure to reduce the start-up time of switching power unit.

According to a further aspect in the invention, switching power unit has series circuit, and this series circuit comprises the primary coil of transformer and be connected main switching device between the positive and negative power line that wherein the positive-negative power line is connecting DC power supply.Switching power unit carries out switching manipulation according to main switching device and exports required direct current voltage in the feedback signal that comparative result between direct voltage that the high frequency voltage rectifier of the secondary coil of transformer induction obtains and the predefined reference voltage obtains by the control main switching device.Here, the signal level of feedback signal is compared with the signal level of the oscillator signal that produces in advance.According to result relatively, definite conducting state duty ratio that will be fed into the drive signal of main switching device, and carry out in pulse strobe switch control and the switch motion between the switch control continuously.In addition, when stopping the switching manipulation of main switching device, stop to provide the working power that drives main switching device with the pulse strobe switch control mode.

In switching power unit according to the present invention, according to the comparative result between the signal level of signal level that produces oscillator signal in advance and feedback signal, definite conducting state duty ratio that will be fed into the drive signal of main switching device.This just might control the switch of main switching device exactly.In addition, also carry out in pulse strobe switch and the switch motion between the switch continuously according to result relatively.This just might carry out switch exactly.In addition, when the switching manipulation of main switching device is stopped, also stopped being provided for driving the working power of main switching device.This just helps to reduce the electrical source consumption that born when shutdown switch is operated, thereby helps to reduce the power loss of device integral body.

Preferably, the working power that drives the on-off controller of main switching device by opening and closing just can obtain pulse strobe switch and controls.This just helps to reduce the power loss of being born when shutdown switch is operated.

Preferably, when the pulse width modulation controlled integrated circuit was used for on-off controller, capacitor was connected the feedback end points of pulse width modulation controlled integrated circuit and is connecting between the internal electric source end points of internal power cord.

Adopt this structure, under the situation of the phase compensation that is used for the output voltage stabilization control system, adopted by a capacitor and the series circuit that resistor is formed between feedback end points that is connected the pulse width modulation controlled integrated circuit and the negative power line, at this moment, even when pulse switch operating period load current increases suddenly, still the control of pulse strobe switch operation control system might be accelerated as quickly as possible, thereby the decline of the output voltage of switching power unit can be avoided.In addition, might reduce unnecessary power loss in pulse strobe switch operation.

Preferably, when the pulse width modulation controlled integrated circuit used as on-off controller, the series circuit that capacitor and resistor are formed was connected the feedback end points of pulse width modulation controlled integrated circuit and is connecting between the internal electric source end points of internal power cord.

Adopt that this structure, under the situation that is used for the phase compensation of output voltage stabilization control system, adopted by a capacitor and the series circuit that resistor is formed between feedback end points that is connected the pulse width modulation controlled integrated circuit and the negative power line, at this moment, even when pulse switch operating period load current increases suddenly, still the control of pulse strobe switch operation control system might be accelerated as quickly as possible, thereby the decline of the output voltage of switching power unit can be avoided.In addition, might almost obtain phase compensation in the output voltage stabilization system under the situation without any influence in paired pulses gating switch operating characteristic.

Preferably, current regulator comprises a NPN transistor, this transistorized collector electrode is connecting the feedback end points of pulse width modulation controlled integrated circuit, emitter is connecting negative power line by a resistor, be connected the holding wire of feedback signal with base stage, and be connected in series in resistor between NPN transistor base stage and the negative power line and connecting the NPN transistor that collector electrode and base stage link together.

Adopt this structure, even when characteristic changes along with temperature, current regulator can be suppressed at and carry out pulse strobe switch operation and the variation of (load current) scheduled current numerical value during the switch motion between the switching manipulation continuously.This just helps regulated output voltage.

Preferably, when the pulse width modulation controlled integrated circuit uses as on-off controller, also provide the startup adjuster, to proofread and correct the startup of pulse width modulation controlled integrated circuit; The starting switch device also is provided, has been used for the working power that opening and closing offer the signal level checker; First resistor is connecting between the feedback end points and negative power line of pulse width modulation controlled integrated circuit; The signal level checker is according to the check results of the signal level of feedback signal, with operating control signal and inverted feedback signal respectively feed-in can be used as soft start capacitor endpoint controller and the feedback end points that operation/not operation derailing switch uses; The soft start capacitor endpoint controller is connected the soft start capacitor end points of pulse width modulation controlled integrated circuit according to operating control signal and disconnects with negative power line; Start adjuster and detect whether exist feedback signal, if the feedback signal of existing then starts adjuster and is connected with negative power line by the feedback end points of second resistor with the pulse width modulation controlled integrated circuit; Otherwise if there is no feedback signal then starts adjuster and just blocks second resistor; And the starting switch device detects whether exist feedback signal, if the feedback signal of existing, then the starting switch device is opened the working power that offers the signal level checker, otherwise, if there is no feedback signal, then the starting switch device just cuts out the working power that offers the signal checking device.

Adopt this structure, when beginning to start, power supply starts immediately and offers the pulse width modulation controlled integrated circuit, and switching power unit begins switching manipulation.This switching manipulation makes the output voltage of switching power unit increase, and detects feedback signal and produces feedback signal until starting adjuster.Consequently, the startup adjuster also is in parallel second resistor and is connected with first resistor, and the starting switch device begins to provide operating current to the signal level checker.Operating current is provided, the signal level checker is started working, and during the signal level of feedback signal is lower than the voltage voltage of current level verification reference power source, the soft start capacitor endpoint controller makes the soft start capacitor end points of pulse width modulation controlled integrated circuit and negative power line keep disconnecting, thereby makes working power can continue to offer the pulse width modulation controlled integrated circuit.So switch work can be continuous, increase to predetermined numerical value with the output voltage that allows switching power unit.

Therefore, when the load of switching power unit is higher than the voltage level of current level verification reference power source than signal level light and the discovery feedback signal, the soft start capacitor endpoint controller is connected the soft start capacitor end points of pulse width modulation controlled integrated circuit with negative power line, closing the working power that offers the pulse width modulation controlled integrated circuit, thus the switching manipulation of shutdown switch supply unit.Along with the decline of output voltage, when the signal level checker made that operating control signal is comparatively low, the signal level of feedback signal descended, and becoming until it is lower than current level verification reference.This just make the soft start capacitor endpoint controller with the soft start capacitor end points of pulse width modulation controlled integrated circuit and negative power line to disconnection, thereby provide working power to the pulse width modulation controlled integrated circuit.Repeat this sequence of operation to obtain the pulse gate oscillating operation.

On the other hand, when and signal level feedback signal heavier when the load of switching power unit do not reach the reference power source of current level verification, the signal level checker just made the operating control signal step-down.This just makes the soft start capacitor endpoint controller soft start capacitor end points of pulse width modulation controlled integrated circuit can be disconnected mutually with negative power line, to such an extent as to continuous switching manipulation can continue.

Particularly, the startup adjuster that is constituted can disconnect second resistor when starting, and with the feedback end points that is increased in the pulse width modulation controlled integrated circuit and the resistance between the negative power line, thereby makes the current potential on the feedback end points become higher.This has just guaranteed reliable start-up operation.On the other hand, in stable operation, start adjuster and connecting second resistor that is in parallel with first resistor, make that the current potential on the feedback end points of pulse width modulation controlled integrated circuit becomes lower.This just allows the PWN control integrated circuit stable voltage of control switching device output reliably.

Preferably, the starting switch device comprises a NPN transistor, this transistorized collector electrode is connecting on the node between the current sensing resistor of feedback signal line that connects the signal level checker and internal reference voltage line, base stage is connecting phototransistor, and emitter is connecting negative power line.

Adopt this structure, might realize having the starting switch device of ball bearing made using.

Preferably, start adjuster and comprise a NPN transistor, this transistorized collector electrode is connecting the feedback end points of pulse width modulation controlled integrated circuit by second resistor, and base stage is connecting phototransistor by a resistor, and emitter is connecting negative power line.

Adopt this structure, might realize having the startup adjuster of ball bearing made using.

Preferably, when the pulse width modulation controlled integrated circuit used as on-off controller, the startup adjuster also provided the correction to the startup of pulse width modulation controlled integrated circuit; First resistor is connected between the feedback end points and negative power line of pulse width modulation controlled integrated circuit; According to the check results of the signal level of feedback signal, with operating control signal and inverted feedback signal respectively feed-in can be used as soft start capacitor endpoint controller and the feedback end points that operation/not operation derailing switch uses; The soft start capacitor endpoint controller is connected the soft start capacitor end points of pulse width modulation controlled integrated circuit according to operating control signal and disconnects with negative power line; And the startup adjuster detects whether exist feedback signal, if the feedback signal of existing, then starting adjuster just is connected the feedback end points of pulse width modulation controlled integrated circuit by diode and second resistor and opens the working power that offers the signal level checker with negative power line, if instead do not exist feedback signal, then start adjuster and just cut off diode and second resistor and close the working power that offers the signal level checker.

Adopt this structure, when starting beginning, power supply just begins to offer the pulse width modulation controlled integrated circuit immediately, and switching power unit begins switching manipulation.This switching manipulation makes the output voltage of switching power unit increase, and detects feedback signal and produces feedback signal until starting adjuster.Consequently, start adjuster and also connecting second resistor that is in parallel with first resistor, and beginning provides operating current to the signal level checker.Operating current is provided, the signal level checker is started working, and during the signal level of feedback signal is lower than the voltage level of current level verification reference power source, the soft start capacitor endpoint controller makes the soft start capacitor end points of pulse width modulation controlled integrated circuit and negative power line keep disconnecting, thereby makes working power can continue to offer the pulse width modulation controlled integrated circuit.So switching manipulation can be continuous, increase to predetermined numerical value with the output voltage that allows switching power unit.

Therefore, when the load of switching power unit is higher than the voltage level of current level verification reference power source than signal level light and the discovery feedback signal, the soft start capacitor endpoint controller is connected the soft start capacitor end points of pulse width modulation controlled integrated circuit with negative power line, closing the working power that offers the pulse width modulation controlled integrated circuit, thus the switching manipulation of shutdown switch supply unit.Along with the decline of output voltage, when the signal level checker made the operating control signal step-down, the signal level of feedback signal descended, and becoming until it is lower than current level verification reference.This just make the soft start capacitor endpoint controller with the soft start capacitor end points of pulse width modulation controlled integrated circuit and negative power line to disconnection, thereby provide working power to the pulse width modulation controlled integrated circuit.Repeat this sequence of operation to obtain the pulse gate oscillating operation.

On the other hand, when and signal level feedback signal heavier when the load of switching power unit do not reach the voltage level of current level verification reference power source, the signal level checker just made the operating control signal step-down.This just makes the soft start capacitor endpoint controller soft start capacitor end points of pulse width modulation controlled integrated circuit can be disconnected mutually with negative power line, to such an extent as to continuous switching manipulation can continue.

Diode avoids that electric current can flow through the signal level checker in predetermined timing cycle, thereby can avoid the signal level checker unnecessary operation to occur, thereby has higher operating accuracy.

Preferably, start adjuster and comprise a NPN transistor, this transistorized collector electrode is being connected the feedback end points of pulse width modulation controlled integrated circuit by diode with second resistor, base stage is connecting phototransistor by a resistor, and emitter is connecting negative power line.

Preferably, the signal level checker comprises: be used for the voltage divider that reference voltage produces, this voltage divider than electronegative potential on one side resistor be divided into two resistors, node is wherein connecting the soft start capacitor endpoint controller by a diode, and the soft start capacitor endpoint controller is connecting the soft start capacitor end points of pulse width modulation controlled integrated circuit by another diode.

Adopt this structure, be used to produce the resistance of each voltage grading resistor of reference voltage by change, just might be directly and fluctuation width and gating switch cycle with the output voltage of pulse strobe switch operation be set exactly.Particularly, make that the fluctuation width of output voltage can be with to use required width the same wide, this just might reduce the unwanted power consumption in pulse switch is operated.

In addition, another diode can avoid making when switching power unit begins to start high level voltage to be applied to the soft start capacitor end points of pulse width modulation controlled integrated circuit.At this moment because when high level voltage is applied to the soft start capacitor end points, closed the output of pulse width modulation controlled integrated circuit.

Preferably, when the pulse width modulation controlled integrated circuit uses as on-off controller, also provide the starting switch device, be used for the working power that opening and closing offer the signal level checker; Current regulator also is provided, and it is connected between the feedback end points and negative power line of pulse width modulation controlled integrated circuit, is used for adjusting the electric current that the feedback end points is exported according to the signal level of feedback signal; The signal level checker can be used as the soft start capacitor endpoint controller that operation/not operation derailing switch uses according to the check results of the signal level of feedback signal with the operating control signal feed-in; The soft start capacitor endpoint controller is connected the soft start capacitor end points of pulse width modulation controlled integrated circuit according to operating control signal and disconnects with negative power line; And the starting switch device detects whether exist feedback signal, if the feedback signal of existing, the starting switch device is just opened the working power that offers the signal level checker, if there is no feedback signal, then the starting switch device just cuts out the working power that offers the signal level checker.

Adopt this structure, when the startup of switching power unit, current regulator is adjusted at the electric current of the feedback end points of pulse width modulation controlled integrated circuit.So, the switching manipulation that the pulse width modulation controlled integrated circuit makes main switching device carry out to have big conducting state duty ratio, thus and reduce start-up time.In addition, in detecting feedback signal, the starting switch device just begins to provide working power to the signal level checker.In addition, the soft start capacitor endpoint controller according to the output signal of signal level checker with being connected and disconnecting of the soft start capacitor end points of pulse width modulation controlled integrated circuit and negative power line, thereby and opening and closing pulse width modulation controlled integrated circuit.Like this, just might realize having the pulse strobe switch operation of high power supply service efficiency.

Description of drawings

From below in conjunction with preferred embodiment and the discussion with reference to the accompanying drawings, various purposes of the present invention and performance will become more clear, and accompanying drawing comprises:

Fig. 1 is the circuit diagram of first embodiment of the invention switching power unit;

Fig. 2 is the circuit diagram of second embodiment of the invention switching power unit;

Fig. 3 is the circuit diagram of third embodiment of the invention switching power unit;

Fig. 4 is the circuit diagram of fourth embodiment of the invention switching power unit;

Fig. 5 is the circuit diagram of typical circuit structure of switching power unit that is used for the employing FA5511 of reference purpose;

Fig. 6 is the circuit diagram that shows the circuit structure profile of FA5511;

Fig. 7 is the signal waveforms of explanation switching power unit start-up operation shown in Figure 5;

Fig. 8 is the signal waveforms of explanation switching power unit start-up operation shown in Figure 4;

Fig. 9 is the circuit diagram of fifth embodiment of the invention switching power unit;

Figure 10 is the circuit diagram of sixth embodiment of the invention switching power unit;

Figure 11 is the circuit diagram of seventh embodiment of the invention switching power unit;

Figure 12 is the circuit diagram of eighth embodiment of the invention switching power unit;

Figure 13 is the circuit diagram of ninth embodiment of the invention switching power unit;

Figure 14 is the circuit diagram of tenth embodiment of the invention switching power unit;

Figure 15 is the circuit diagram of eleventh embodiment of the invention switching power unit;

Figure 16 is the circuit diagram of twelveth embodiment of the invention switching power unit;

Figure 17 is the signal waveforms of the start-up operation of Figure 16 and switching power unit shown in Figure 19;

Figure 18 is the circuit diagram of thriteenth embodiment of the invention switching power unit;

Figure 19 is the circuit diagram of fourteenth embodiment of the invention switching power unit;

Figure 20 is the circuit diagram of fifteenth embodiment of the invention switching power unit;

Figure 21 is the circuit diagram of sixteenth embodiment of the invention switching power unit; With,

Figure 22 is the circuit diagram of seventeenth embodiment of the invention switching power unit.

Embodiment

Embodiments of the invention hereinafter are discussed with reference to the accompanying drawings.

First embodiment

Fig. 1 is the circuit diagram of the switching power unit of first embodiment of the invention.

In switching power unit shown in Figure 1, transformer 3 has primary coil 4, and an end of this primary coil is connecting positive power line 1, and its other end is connecting negative power line 2 by main switching device 5.Main switching device 5 can adopt for example FET (field-effect transistor).Transformer 3 has secondary coil 6, and an end of this secondary coil is connecting output line 25 by diode 7, and its other end is connecting output line 26.Between

output line

25 and 26, have the capacitor 45 and the output voltage detector circuit 9 that are connecting.Output voltage detector circuit 9 is connecting the input of signal level checker circuit 15 and the input of on-off controller circuit 19 by line 9a, with each input of feedback signal feed-in.

Working power 16 has the negative terminal that is connecting negative power line 2, with the anode that is being connected signal level checker circuit 15 and switching circuit 17 inputs by line 16a.Signal level checker circuit 15 is by the control end of line 15a with operating control signal feed-in switching circuit 17.The output of switching circuit 17 is connecting the power end of on-off controller circuit 19 by line 17a.The output of on-off controller 19 is connecting the control end of main switching device 5.

The operation of the switching power unit of first embodiment then, is discussed.When the voltage from the DC power supply that does not have explanation was applied between positive and

negative power line

1 and 2, main switching device 5 was carried out switching manipulation under the control of on-off controller circuit 19, thereby makes high-frequency current flow through the primary coil 4 of transformer 3.This produces high frequency voltage in the secondary coil 6 of transformer 3.This high frequency voltage is by diode 7 rectifications, and is level and smooth by capacitor 45 subsequently, thereby converts direct voltage to.This direct voltage is applied between

output line

25 and 26, exports in the output voltage mode of switch element device.

Output voltage detector circuit 9 will be compared with preset reference voltage at the output voltage between

output line

25 and 26, and be fed into signal level checker circuit 15 and on-off controller circuit 19 with the result that the mode of feedback signal will compare by line 9a.On-off controller circuit 19 is worked from working power 16 power supply that provides by switching circuit 17, and carry out control according to feedback signal by the timing of control opening and closing main switching device 5, the needed direct voltage of output between

output line

25 and 26 by this way.

When being connected the very little electrical power (that is, at light load operation) of load consumption between the output line 25 and 26 (output of switching power unit), the output voltage between output line 25 and 26 (output of switching power unit) just trends towards higher.In order to proofread and correct this trend, output voltage detector circuit 9 has such as the feedback signal of high level more to line 9a output.

On the other hand, when being connected the big electrical power of load consumption between output line 25 and 26 (that is, in the heavy duty operation), the output voltage between

output line

25 and 26 trends towards lower.In order to proofread and correct this trend.Output voltage detector circuit 9 has such as more low level feedback signal to line 9a output.

When the output voltage between output line 25 and 26 (output voltage of switching power unit) is higher than reference voltage and the feedback signal output by line 9a output and has higher level, signal level checker circuit 15 just passes through line 15a to switching circuit 17 feed-in operating control signals, thus off switch circuit 17.

When switching circuit 17 cut out, ON-OFF control circuit 19 output voltage that power supply 16 is provided that just quits work was so just stopped operation.Consequently, main switching device 5 shut-down operations are so allow the output voltage (output voltage of switching power unit) between

output line

25 and 26 progressively to descend.

Along with the decline of output voltage, the level of the feedback signal of output voltage detector circuit 9 outputs just becomes such as lower.Subsequently, signal level checker circuit 15 to switching circuit 17 feed-in operating control signals, is a switching circuit 17 thereby open by line 15a.This feasible voltage from working power 16 can offer on-off controller circuit 19, and on-off controller circuit 19 resume operations, and makes main switching device 5 carry out switching manipulations.

Therefore, the output voltage between output line 25 and 26 (output voltage of switching power unit) increases, and output voltage detector circuit 9 passes through the feedback signal of line 9a to signal level checker circuit 15 feed-in higher level simultaneously.Subsequently, signal level checker circuit 15 off switch circuit 17 with the operation of shutdown switch control circuit 19, thereby and stop the switching manipulation of main switching device.

When being connected load between

output line

25 and 26 is heavy duty and when consuming considerable electrical power, and output voltage just trends towards quite low.Under these circumstances, the 17 continuation conductings of signal level checker circuit 15 maintained switch circuit.So on-off controller circuit 19 makes main switching device 5 carry out switching manipulation continuously, thus and regulated output voltage.

As discussed above, can be by repeating when the output voltage of switching power unit increases, the shutdown switch operation, and when output voltage descends, the operation that restarts switch obtains pulse strobe switch and operates.This has just stablized output voltage.

In pulse strobe switch operation, can not provide the working power of signal level checker circuit 15 under the condition by switching circuit 17, and therefore making signal level checker circuit 15 keep operation, even during the shutdown switch operation.Yet the power consumption of signal level checker level 15 is much smaller than the power consumption of on-off controller circuit 19, and therefore switching power unit carries out work with lower power consumption, and then can save energy.

Second embodiment

Fig. 2 is the circuit diagram of the switching power unit of second embodiment of the invention.

In switching power unit shown in Figure 2, transformer 3 has primary coil 4, and an end of this primary coil is connecting positive power line 1, and its other end is connecting negative power line 2 by main switching device 5.Transformer 3 has secondary coil 6, and an end of this secondary coil is connecting output line 25 by diode 7, and its other end is connecting output line 26.Between

output line

25 and 26, have the capacitor 45 and the output voltage detector circuit 9 that are connecting.

Output voltage detector circuit 9 is made up of two series circuits that are connected between

output line

25 and 26, in particular, one of them is by photoelectrical coupler 20, resistor 21, form with shunting adjuster 22, another then is made up of output voltage voltage grading resistor 23 and 24.Photoelectrical coupler 20 comprises photodiode 20a and phototransistor 20b.The control end points of shunting adjuster 22 is connected on the node between output voltage voltage grading resistor 23 and 24.Shunting adjuster 22 will be compared with the reference voltage that is provided with in inside in advance at the voltage on the node between output voltage

voltage grading resistor

23 and 24, and allow to adopt the electric current comparative result that flows through photodiode to come offset current.

Working power 16 has negative terminal that is connecting negative power line 2 and the anode that is being connected steady operation current power supply line 16a.Signal level checker circuit 15 is by Zener diode 191, resistor 201, and comparator 18 and current sensing resistor 28 are formed.

The negative electrode of Zener diode 191 is connected with steady operation current power supply line 16a, with and anode be connected with an end of resistor 201 and the inverting input of comparator 18.The other end of resistor 201 is connecting negative power line 2.One end of current sensing resistor 28 is connecting steady operation current power supply line 16a, and its other end is connecting the collector electrode of the phototransistor 20b of the inverting input of comparator 18 and photoelectrical coupler 20.

The positive power source terminal of comparator 18 is connecting steady operation current power supply line 16a, and its negative power end is connecting negative power line 2.The output of comparator 18 is connecting the control end of switching circuit 17 by line 15a.The emitter of phototransistor 20b is connecting the control end of on-off controller circuit 19 by line 19a.The output of on-off controller circuit 19 is connecting the control end of main switching device 5.

The operation of the switching power unit of second embodiment then, is discussed.When the direct voltage of working power 16 outputs was applied between the positive and

negative power line

1 and 2, under the control of on-off controller circuit 19, main switching device 5 was carried out switching manipulation, thereby produces the high-frequency current of the primary coil 4 that flows through transformer 3.This just induces high frequency voltage in the secondary coil 6 of transformer 3.This high frequency voltage adopts diode 7 rectifications, and adopts capacitor 45 level and smooth subsequently, thereby converts direct voltage to.This direct voltage is applied between

output line

25 and 26, makes it the output voltage output as switching power unit.

Output voltage detector circuit 9 is compared the output voltage between

output line

25 and 26 with predetermined reference voltage, and with the mode of this comparative result with feedback signal, on the one hand by the node FD feed level checker circuit 15 between phototransistor 20b and current sensing resistor 28, on the other hand by line 19a feed-in on-off controller circuit 19.

In particular, in output voltage detector circuit 9, shunting adjuster 22 will be compared with the reference voltage of inner preparation in advance at the node voltage between output voltage

voltage grading resistor

23 and 24, and produce the compensation of electric current with the comparative result that flows through photodiode 20a.Phototransistor 20a provides and flows through the electric current that the electric current that flows into on-off controller circuit 19 by current sensing resistor 28 behind the photodiode 20a is complementary from working power 16.So, according to the electric current that is provided, the switching manipulation of on-off controller circuit 19 control main switching devices 5, thereby and the output voltage of control switching device (voltages between output line 25 and 26), make the numerical value that it can equal to be scheduled to.

In signal level checker circuit 15, comparator 18 is compared the voltage drop on the current sensing resistor 28 with the voltage of the current level verification reference power source that is produced by Zener diode 191 and resistor 201, and will pass through line 15a feed-in switching circuit 17 with the signal that comparative result is complementary.Zener diode 191 can adopt resistor to replace.

When the less electrical power of the load consumption that is connected (output of switching power unit) between output line 25 and 26 (that is, in light load operation), then the output voltage between output line 25 and 26 (output voltage of switching power unit) just trends towards higher.In order to proofread and correct this trend, output voltage detector circuit 9 just increases the electric current that flows through phototransistor 20b.

Comparator 18 is according to the current value and the result who is compared by the set reference current levels of current level verification reference power source that flow through phototransistor 20b, the operating control signal of output high level, and by the control end of line 15a, thereby off switch circuit with this high level operating control signal feed-in switching circuit 17.This just stops to provide supply voltage to on-off controller circuit 19, thereby on-off controller circuit 19 will quit work.Therefore, main switching device 5 quits work, so the output voltage of switching power unit reduces gradually.

Along with the reduction of output voltage, the current value that flows through phototransistor 20b also reduces.Subsequently, comparator 18 is according to the current value and the result who is compared by the set reference current levels of current level verification reference power source that flow through phototransistor 20b, the operating control signal of output low level, and, thereby open switching circuit by the control end of line 15a with this low level operating control signal feed-in switching circuit 17.This just begins to provide supply voltage to on-off controller circuit 19.So on-off controller circuit 19 begins operation.Therefore, main switching device 5 is started working, and the output voltage of switching power unit just increases gradually.

Along with the increase of output voltage, the current value that flows through photodiode 20b also can increase.Subsequently, comparator 18 is according to the current value and the result who is compared by the set reference current levels of current level verification reference power source that flow through phototransistor 20b, the operating control signal of output high level, and by the control end of line 15a, thereby off switch circuit with this high level operating control signal feed-in switching circuit 17.This just stops to provide supply voltage to on-off controller circuit 19, thereby on-off controller circuit 19 will quit work.Therefore, main switching device 5 quits work, so the output voltage of switching power unit reduces gradually.Afterwards, just repeat this control sequence, thereby and keeping pulse gate vibration.Like this, the output voltage of switching power unit just keeps substantially constant.

By the way, in the above-mentioned operation of discussing, these belong to first's content of the sequence of above-mentioned discussion, that is: switching circuit 17 closes, stopping of the switching manipulation of main switching device 5, the reduction of output voltage, the electric current that flows through phototransistor 20b reduces, and the output of the low level signal of comparator 18 outputs, do not carry out simultaneously; But, because the delay that the circuit various piece is produced, just need certain operating time so carry out all these operations, and in the time durations of this operation, the work of switching power unit shutdown switch.

Equally, belong to the operation of the above-mentioned second portion of discussing, promptly, the unlatching of switching circuit 17 starts the switching manipulation of main switching device 5, the increase of output voltage, the electric current that flows through phototransistor 20b increases, and the output of the high level signal of being exported from comparator 18 is not carried out simultaneously; But, because the delay that the circuit various piece is produced, just need certain operating time so carry out all these operations, and in the time durations of this operation, the continuous switch work of switching power unit.

Keep carrying out and stopping to carry out in the switching manipulation cycle at switching power unit, the theory of above-mentioned operating time of discussing helps not only to be applied to this embodiment can also use first embodiment.

In control, voltage level feed-in by the current level verification reference power source that will reduce slightly in off switch circuit 17 is 18 non-inverting input relatively, equally, voltage level feed-in by the current level verification reference power source that will increase slightly when opening switching circuit 17 is 18 non-inverting input relatively, can introduce slow phenomenon in a small amount.This helps to prolong the cycle that switching power unit keeps carrying out and stopping to carry out the switching manipulation cycle.

On the other hand, when the big electrical power of load consumption (that is, in the heavy duty operation) that is connected between

output line

25 and 26, the output voltage between

output line

25 and 26 just trends towards lower.This can cause that the electric current that flows through phototransistor 20b descends, and causes therefore that voltage drop on the current sensing resistor 28 becomes and be lower than voltage drop on the Zener diode 191.Therefore, comparator 18 output low level operating control signals so switching circuit 17 keeps continuous operation, allow switching power unit to carry out continuous switching manipulation.

Here, it should be noted,, just can obtain the pulse strobe switch operation according to the comparative result between current value that flows through phototransistor 20b and reference current value (voltage drop at Zener diode 191 two ends is transformed into current value).The load current value of the signal level of the feedback signal of output voltage detector circuit 19 (that is, flowing through the current value of phototransistor 20b) expression switching power unit.So, just might correctly be set in the load current value of carrying out switch between continuous switching manipulation and the pulse switch operation.

In the pulse strobe switch operation, as previous the discussion, output voltage can fluctuate.Yet, because the signal level of feedback signal, promptly, flow through the current value of phototransistor 20b, the output voltage values that also can represent switching power unit, that will continue just as discussed above and later on to discuss is such, and the upper and lower bound value of output voltage just might correctly be set.

The signal level of feedback signal can detect on the line 19a of the control end that connects on-off controller circuit 19.Yet such just as will be discussed, this structure not can do with the situation of on-off controller circuit 19 by its control end outflow electric current.Promptly, when having offered the working power opening and closing of on-off controller circuit 19, the voltage value on control end changes by the current value that control end flowed out, so just can not correctly be represented output voltage and load current as discussed above.

Like this, by repeating shutdown switch operation when the output voltage of switching power unit increases, just can obtain the pulse strobe switch operation and when output voltage descends, restart switching manipulation.This helps regulated output voltage.

In the pulse strobe switch operation, do not provide working power to signal level checker circuit 15 by switching circuit 17, therefore, even when switching manipulation stops, signal level checker circuit 15 is still keeping working.Yet the power consumption of signal level checker circuit 15 is much smaller than the power consumption of on-off controller circuit 19, and therefore, the effect of saving the energy has been played in the power consumption work that switching power unit can be very little.

The 3rd embodiment

Fig. 3 is the circuit diagram of the switching power unit of third embodiment of the invention.Fig. 3 is the circuit diagram that shows the detailed circuit structure of working power 16 illustrated in figures 1 and 2, in Fig. 3, all adopts identical reference number to identify with this class circuit element similar among Fig. 1 and Fig. 2, and no longer repeats the explanation to them.

At Fig. 3, the working power of on-off controller circuit 19 is provided by starting current power line 29a and steady operation current power supply line 16a, wherein, starting current is provided by startup resistor 29 by positive power line 1, and the voltage of induction on transformer 3 ancillary coils 32 can be provided by a plurality of

diodes

30 and 31 series circuits of being formed by steady operation current power supply line 16.The working power of the phototransistor 20b of signal level checker 15 and photoelectrical coupler 20 is to provide from the auxiliary control source that is extracted by node between

diode

30 and 31.

Corresponding to the circuit of original working power of discussing 16 are ancillary coils 32 by transformer 3, diode 31, and capacitor 33, diode 30, startup resistor 29 and capacitor 46 are formed.In switching power unit, when beginning to start, when the direct voltage by undeclared DC power supply output is applied between positive and

negative power line

1 and 2, charge current flows to capacitor 46 by startup resistor 29, and just as discussed below, because switching circuit 17 conductings, when the charging voltage of capacitor 46 can reach predetermined voltage level, on-off controller circuit 19 was just started working and is begun drive signal is offered main switching device 5.

So switching power unit begins switch work, and on the ancillary coil 32 of transformer 3, induce high frequency voltage.This high frequency voltage is through the rectification of diode 31 and capacitor 33 and level and smooth, and changes into direct voltage.The work of phototransistor 20b and comparator 18 is to provide working power by capacitor 33, and adopts output voltage with switching power unit to remain on the mode of predetermined value and carry out work as previous institute the discussions mode that like that the employing pulse strobe switch is controlled than gently the time when load.

In the start-up operation process of switching power unit, diode 30 prevents to flow to capacitor 33 from the electric current of positive power line 1 by startup resistor 29, and therefore, this helps shortening capatcitor 46 charging voltages to reach the required time of predetermined voltage level.After finishing the start-up operation of switching power unit, pass through the electric current of diode 30 when the charging current of capacitor 46 is main from capacitor 33, and provide working power to on-off controller circuit 19 by switching circuit 17.

When switching power unit began to start, the charging voltage of capacitor 33 was zero, so comparator 18 is not worked.Yet, because the output of comparator 18 is subjected to the drop-down of resistor 62, so switching circuit 17 is in opening.

Equally, when Switching Power Supply began to start, the charging voltage of capacitor 33 was zero, does not therefore just have electric current to flow through phototransistor 20b.So, suppose that the output voltage of switching power unit is lower than predetermined voltage, then on-off controller circuit 19 control main switching devices 5.Therefore, when switching power unit began to work under predetermined stable state, along with the output voltage increase of switching power unit, the charging voltage of capacitor 33 just increased, and can flow through phototransistor 20b until electric current.

As discussed above, in it began cycle with steady state operation, on-off controller circuit 19 and switching circuit 17 came work by the charging voltage of using capacitor 46 as working power after switching power unit begins to start.Therefore, be lower than the minimum that is allowed for the charging voltage that can prevent capacitor 46 becomes in this cycle, capacitor 46 just need have very high capacitance.

By increasing the resistance of startup resistor 29, just might reduce power consumption by startup resistor 29.Yet, when switching power unit begins to start,, slowed down its startup if make the too high elongation that will cause of this resistance to capacitor 46 charging required times.

In this embodiment, when switching power unit started, diode 30 prevented that the flow of charge that capacitor 46 is accumulated from going into phototransistor 20b and comparator 18.This helps to reduce to start the required time.Yet,, might reduce the consumption of power by increasing the resistance of startup resistor 29.

In the switching power unit of this embodiment, the mode that signal level checker circuit 15 provides the line of working power to come the opening and closing switching circuit by the repetition opening and closing to on-off controller circuit 19 obtains pulse strobe switch control.In addition, in pulse strobe switch control, when the switch work of main switching device 5 stops, also stopped providing working power to ON-OFF control circuit 19.This just helps to reduce the power loss of being born when shutdown switch is worked, also help to reduce the power consumption of device integral body.

The 4th embodiment

Fig. 4 is the circuit diagram of the switching power unit of fourth embodiment of the invention.In Fig. 4, all adopt identical reference number to identify with this class circuit element similar among Fig. 1 to Fig. 3, and no longer repeat explanation them.The switching power unit of this embodiment has adopted pulse-width modulation (pulse width modulation) control integrated circuit, and for example, the production code member that can adopt Fuji electronics corporation to be produced is the integrated circuit of FA5511.In Fig. 4, FA5511 is shown in integrated circuit 38.

Fig. 6 is the construction profile figure of FA 5511.In Fig. 6, when working power was provided at the Vcc end, this working power had just offered output buffer 101, the voltage adjuster 103 of arithmetic control circuit 102 and 5V.When being higher than the predetermined work starting resistor by the Vcc end voltage that T6 provided, 5V adjuster 103 just enters into the output enable state, and stable 5V power supply is provided, on the one hand, offers pulse-width modulation logical circuit 105 and OSC (oscillating circuit) 106 by internal power cord 104; On the other hand, offer feedback end T2 by internal power cord 104 and by diode 107 and resistor 108.

Internal electric source end T7 is connecting internal power cord 104, and this internal electric source end T7 outside is connecting capacitor 40, to eliminate the noise that internal power cord 104 is produced.This capacitor 40 can prevent that noise is superimposed upon institute by internal power cord 104 and provides on the power supply, thereby can prevent the control that makes mistakes.

The frequency of oscillation of OSC 106 is to be provided with by the resistance of resistor 36, and this resistor is externally connecting end points T1.The oscillator signal that OSC 106 is produced is fed into pulse-width modulation logical circuit 105.The series circuit that feedback end T2 is formed by diode 107 and resistor 108 is pulled to internal power cord 104, therefore, provides the voltage of series circuit with the external circuit elements institute dividing potential drop that is being connected feedback end T2 to pulse-width modulation logical circuit 105.

The mode that will discuss below pulse-width modulation logical circuit 105 adopts, the voltage level of feedback end T2 and the voltage level of soft start capacitor end T8 are carried out logical calculated (this will discuss following), and from the oscillator signal of 106 feed-ins of OSC, and drive signal feed-in output buffer 101 (see figure 4)s that will be used to drive main switching device 5.Output buffer 101 electric currents amplify this drive signal, and subsequently it as drive signal feed-in main switching device 5, main switching device connects by output T5 is outside.

By end T3, feed-in is from the current detection signal of main switching device 5.When the electric current that flows through main switching device 5 has surpassed predetermined level, then pulse-width modulation logical circuit 105 is just closed the drive signal (being decreased to low level) of main switching device with protection main switching device 5.End T7 is used as the common ground end of FA 5511 internal circuits, and is connecting the negative power line (see figure 4) of switching power unit.

Capacitor 41 outsides are connecting soft start capacitor end T8.As discussed above, in 5V voltage adjuster 103 outputs one output enable signal, arithmetic control circuit 102 is fed into capacitor 41 with weak current at arithmetic control circuit 102, and capacitor 41 charges gradually like this.When the switching power unit steady state operation, arithmetic control circuit 102 is just controlled the charging voltage of this capacitor 41, makes it can not surpass predetermined voltage level.

When the current potential of soft start capacitor end T8 externally forces step-down under the effect of circuit, arithmetic control circuit 102 is just forbidden 103 work of 5V adjuster, thereby stop to provide power supply to

internal power cord

104,5V voltage adjuster 103 is to output buffer 101 output inhibit signals simultaneously.So, when the current potential of soft start capacitor end T8 externally forces step-down under the effect of circuit, just reduced the power that FA 5511 is consumed greatly.

The switching power unit of this embodiment has been opened up the above-mentioned functions of FA 5511.Particularly, when the output voltage of switching power unit when being high, then the signal level of feedback signal also is high, the current potential that signal level checker circuit 15 (see figure 5)s just force soft start capacitor end T8 is step-down under the circuit function externally, thereby can stop the work of output buffer 101, pulse-width modulation logical circuit 105 and OSC 106.This just makes switching power unit to quit work, and this is the result of the signal level reduction of feedback signal.After this, signal level checker circuit 5 stops to force the current potential step-down of soft start capacitor end T8, thereby restarts switching power unit.Like this, under the underloaded condition of work of switching power unit, just can obtain the pulse strobe switch operation.

For the purpose of reference, Fig. 5 has shown the circuit structure that adopts the switch element device of FA 5511 typical circuit structures.In Fig. 5, all adopt identical reference number to identify with this class circuit element similar among Fig. 4, and no longer repeat explanation them.Fig. 7 has shown after switching power unit begins to start during beginning with steady state operation in the observed signal waveform of reference point.In Fig. 7, shown voltage 701 at capacitor shown in Figure 5 46 two ends at (a); Shown the voltage 702 on the feedback end T2 of integrated circuit 38 shown in Figure 5 at (b), oscillator signal 702 (see figure 6)s of the OSC 106 of feed-in pulse-width modulation logical circuit 105, and the voltage 704 on soft start capacitor end T8; Shown the output signal of exporting by output T5 705 at (c).

Now, with reference to Fig. 5 and Fig. 7, the operation of switching power unit is discussed.At first, when time point t0, direct voltage is applied between positive and

negative power line

1 and 2, owing to the effect of the charging current that is provided by startup resistor 29, the voltage 701 at capacitor 46 two ends increases gradually, when time point t1, when voltage reaches the predetermined work starting voltage of FA 5511, then the voltage on the internal power cord 104 of integrated circuit 38 inside rises, as discussed above, so OSC 106, pulse-width modulation logical circuit 105 and output buffer 101 are just started working.

So, OSC 106 will have the oscillator signal feed-in pulse-width modulation logical circuit 105 of constant upper and lower bound and constant cycle, and as the result of capacitor 41 to charge from the weak current of 102 feed-ins of arithmetic control circuit, then the voltage on soft start capacitor end T8 just increases gradually.When time point t1, the voltage between

output line

25 and 26 still is zero, therefore, does not just have electric current can flow through shunting adjuster 22 and phototransistor 20b.So the voltage 702 on the feedback end T2 of integrated circuit 38 is high.

When no matter the voltage 702 of the voltage 704 of soft start capacitor end T8 and feedback end T2 be that pulse-width modulation logical circuit 105 is all exported the output signal (pulse signal) 705 that its level is higher than the output T5 voltage of output buffer 101 when being lower than or being higher than the oscillator signal 703 that OSC 106 exported.So, process from time point t1 to time point t2, be lower than at the level of the voltage 704 of soft start capacitor end T8 the oscillator signal that OSC106 exports level during, output signal 705 is just kept low.At time point t2, when the level of the voltage 704 of soft start capacitor end T8 is instantaneous when surpassing the level of oscillator signal 703 of OSC 106, output signal 705 just becomes height, and for keeping high the period of correspondence, to open main switching device 5.

Afterwards,, remain at output voltage 705 and just become more and more longer high period, then be provided at the corresponding increase of power between

output line

25 and 26 by diode 7 from the secondary coil 6 of transformer 3 along with voltage 704 increases.So the voltage between

output line

25 and 26 increases, until at time point t3 the time, when the voltage 702 at feedback end T2 began to descend, electric current began to flow through shunting adjuster 22 and phototransistor 20b.

Then, at time point t5, when the voltage 702 at feedback end T2 becomes when being lower than voltage 704 at soft start capacitor end T8, the level of the oscillator signal 703 of OSC106 and the comparative result between the voltage 702 on the feedback end T2 can be determined to be high period at the output voltage 705 of output T5.Because the level of voltage 702 is represented the output feedback signal of output voltage detector circuit 9, so switching power unit begins to carry out work with the stable state of output predetermined voltage now.

On the other hand, during cycle from time point t1 to time point t3, the charging voltage 701 of capacitor 46 trends towards progressively reducing, because in this cycle, the electric current that flows into Vcc end T6 is more than the electric current that is provided by startup resistor 29.Yet, having fully high electric capacity by making capacitor 46, this reduces the minimum work Vcc voltage that can Be Controlled must be unlikely to become and be lower than integrated circuit 38 (that is, FA 5511).

As discussed above, the output voltage of switching power unit increases, and begins to increase in capacitor 46 charging voltages 701 of time point t4 correspondence, to reach the burning voltage of stable state at time point t6.

It should be understood that, the circuit structure of the switching power unit of explaining with reference to Fig. 5 only is an example that adopts the typical circuit structure of FA5511, so this example does not comprise the function of the pulse strobe switch that is obtained with this specific embodiments under the situation of light load operation discussed below.

The work of switching power unit embodiment illustrated in fig. 4 then, is discussed with reference to signal waveforms shown in Figure 8.In Fig. 8, shown voltage 801 on the capacitor shown in Fig. 4 46 at (a); Be presented at the integrated circuit 38 shown in Fig. 4 (promptly at (b), FA 5511) the voltage 804 of feedback end T2, the oscillator signal 803 and the voltage 805 on the soft start capacitor end T 8 of integrated circuit 38 of OSC106 (see figure 6) feed-in pulse-width modulation logical circuit 105 (see figure 6)s; Shown the output signal of exporting by integrated circuit 38 output T5 806 at (c).

At first, when time point T0, direct voltage is applied between positive and

negative power line

1 and 2, owing to the effect of the charging current that is provided by startup resistor 29, the voltage 801 at capacitor 46 two ends increases gradually, when time point T1, when voltage reaches the predetermined work starting voltage of FA 5511, then the voltage on the internal power cord 104 of integrated circuit 38 inside rises, as discussed above, so, OSC106, pulse-width modulation logical circuit 105 and output buffer 101 are just started working.

So, OSC 106 will have the oscillator signal feed-in pulse-width modulation logical circuit 105 of constant upper and lower bound and constant cycle, and as the result of capacitor 41 to charge from the weak current of 102 feed-ins of arithmetic control circuit, then the voltage on soft start capacitor end T8 just increases gradually.When time point T1, the charging voltage of capacitor 33 is zero, the output current of signal level checker circuit 15 is zero, and, to discuss as later, the switch that starts correcting circuit 35 is then cutting out.Therefore, the voltage 804 on the feedback end T2 of integrated circuit 38 is branch pressure voltages, and it is the diode 107 that integrated circuit 38 inside are provided, the (see figure 4) as a result of the voltage dividing potential drop of resistor 108 and resistor 39a.

This branch pressure voltage is set to be higher than a little the lower voltage limit level of oscillator signal 803.

When no matter the voltage 804 of the voltage 805 of soft start capacitor end T8 and feedback end T2 be that pulse-width modulation logical circuit 105 is by output signal 806 of output T5 output of output buffer 101 when being lower than or being higher than the oscillator signal 803 that OSC 106 exported.

So, during cycle from time point T1 to time point T2, voltage 805 level of soft start capacitor end T8 be lower than the oscillator signal 703 that OSC 106 exported level the time interim, output signal 806 keeps low.At time point T2, when the level of the voltage 805 of soft start capacitor end T8 is instantaneous when surpassing the level of oscillator signal 803 of OSC 106, then output signal 705 becomes and is height, and still keeps high subsequently in the corresponding cycle, to open main switching device 5.

This just makes the voltage between

output line

25 and 26 to increase a little, and can make the charging voltage of capacitor 33 increase in the mode that increases corresponding to voltage between output line 25 and 26.Therefore, beginning provides electric current by signal level checker 15 to the feedback end T2 of integrated circuit 38 from capacitor 33, so begin to increase at the voltage 804 of feedback end T2.

When the electric current that flows through phototransistor 20b during less than predetermined value set in signal level checker circuit 15, signal level checker circuit 15 provides electric current to the feedback end T2 of integrated circuit 38; On the contrary, when the electric current that flows through phototransistor 20b during greater than predetermined value set in signal level checker circuit 15, then signal level checker circuit 15 does not still provide any electric current to feedback end T2 and soft start capacitor end T8 just to soft start capacitor side controller circuit 37 feed-in electric currents.

At signal level checker circuit 15 when the feedback end T2 of integrated circuit 38 provides electric current, when the current values that flows through phototransistor 20b increases, then signal level checker circuit 15 just reduces supplying electric current (inverted feedback signal), on the contrary, when the current value decline of flowing through phototransistor 20b, then signal level checker circuit 15 just increases supply current (inverted feedback signal).

Supply current also depends on the working power of signal level checker circuit 15, that is, it also depends on the charging voltage of capacitor 33.So, go through as above, after switching power unit began to start, along with the voltage between

output line

25 and 26 increases, and along with the increase of the charging voltage of capacitor 33, supply current also increased.

Afterwards, when supply current increases until arriving steady-working state, voltage in this state between the

output line

25 and 26 is stable, the charging voltage of voltage between the

output line

25 and 26 and capacitor 33 is stabilized in steady state value, and this steady state value is than determined by the secondary coil 6 of the output voltage of switching power unit and transformer 3 and the coil windings between the ancillary coil 32.So supply current only depends on the current value that flows through phototransistor 20b now, as discussed above.

Then, after time point T2, increase along with the voltage 805 of soft start capacitor end T8, keep the high cycle will become more and more longer in output signal 806 by output T5 output, so, voltage between

output line

25 and 26 will increase, and the charging current of capacitor 33 also can increase, so the electric current that signal level checker circuit 15 is provided also can increase.Just because of the result that this situation takes place, the voltage 804 of feedback end T2 also can increase gradually.

After time point T3, when the voltage 805 of soft start capacitor end T8 becomes when being higher than the voltage 804 of feedback end T2, as discussed above, pulse-width modulation logical circuit 105 is just compared the voltage 804 of feedback end T2 with the oscillator signal 803 of OSC 106, and according to result relatively, output T5 by output buffer 101 exports this output signal 806, makes this output signal 806 as drive signal feed-in main switching device 5.

As discussed above, the charging voltage of capacitor 33 depends on voltage and the secondary coil 6 of transformer 3 and the ratio of winding between the ancillary coil 32 between output line 25 and 26.So after time point T2, along with the voltage between

output line

25 and 26 increases, the charging voltage of capacitor 33 also increases, and is described as curve shown in Fig. 8 (a) thereupon.At time point T4, when becoming, the voltage of capacitor is higher than when starting predetermined value set in the Correction circuit 35, and start Correction circuit 35 switch that is provided just is provided, make resistor 39b and resistor 39a be connected in parallel.

Therefore, in the instantaneous decline of voltage 804 meetings of feedback end T2, still, because the voltage level after descending is higher than the lower limit of oscillator signal 803, though so understand instantaneous shortening in the high level period of output T5 output signal 806, main switching device 5 still continues switching manipulation.So the charging voltage of voltage between

output line

25 and 26 and capacitor 33 still can continue to increase, and begins to increase once more at the voltage of feedback end T2.

Instantaneous before time point T6, when the comparison referential data that is provided in shunting adjuster 22 has been provided the voltage that voltage divider produced of

resistor

23 and 24, electric current just begins to flow through shunting adjuster 22, photodiode 20a and phototransistor 20b.So the source current of signal level checker circuit 15 output just stops to increase, also stop to increase at the voltage 804 of feedback end T2, and switching power unit begins with steady state operation.

In steady shape work, for example, when the voltage between

output line

25 and 26 increases, the voltage of the voltage divider output that resistor 23 and 24 is formed also increases, then flow through shunting adjuster 22, the electric current of photodiode 20a and phototransistor 20b also increases, therefore the supply current of signal level checker circuit 15 will reduce, voltage 804 at feedback end T2 also reduces, then pulse-width modulation logical circuit 105 is compared the oscillator signal 803 of OSC 106 and is finally exported the output signal (drive signal) 806 of high level period shortening by the output T5 of integrated circuit 38 with the voltage 804 of feedback end T2, therefore so it is shorter that the duty ratio of the conducting state of main switching device 5 will become, the electric current that flows to output line 25 by diode 7 reduces.The result that this process takes place makes that the voltage between

output line

25 and 26 reduces.

Compare, when the voltage between

output line

25 and 26 descends, the voltage of the voltage dividing potential drop of being made up of

capacitor

23 and 24 also can descend, so flow through shunting adjuster 22, the electric current of photodiode 20a and phototransistor 20b also can reduce, so increased the supplying electric current of signal level checker circuit 15, therefore the voltage 804 at feedback end T2 will increase, then pulse-width modulation logical circuit 105 is just compared the oscillator signal 803 of OSC106 with the voltage 804 of feedback end T2, and finally the output T5 by integrated circuit 38 exports the output signal (drive signal) 806 that high level period is elongated, so it is longer that the duty ratio of the conducting state of main switching device 5 will become, therefore flow to the electric current increase of output line 25 by diode 7.The result that this process takes place makes that the voltage between

output line

25 and 26 increases.

Through this sequence of operation, just be stabilized on the predetermined numerical value at the voltage between output line 25 and 26.Thereby the charging voltage of capacitor 33 is also stable, so the magnitude of current that signal level Correction circuit 15 is provided only depends on the electric current that flows through phototransistor 20b.

When switching power unit starts and this device during with steady state operation between, start Correction circuit 35 and switch in the feedback end T2 of integrated circuit 38 and the resistance between the negative power line 2.This has guaranteed that switching power unit can carry out switching manipulation reliably.

Particularly, when switching power unit began to start, the charging voltage of capacitor was zero, and the electric current that signal level checker circuit 15 is provided also is zero.Therefore, resistor 39a presents high resistance, as discussed above, so have diode 107 by integrated circuit 38 inner institutes, the voltage that the voltage dividing potential drop that resistor 108 and resistor 39a (see figure 4) are formed produces is higher than the lower limit of OSC 106 oscillator signals.

If not this situation, even after the voltage level of the soft start capacitor end T8 of integrated circuit 38 increases, still be lower than the lower limit of the oscillator signal of OSC 106 at the voltage level of feedback end T2, so pulse-width modulation logical circuit 105 just can not be by output T5 output high level signal.This just can not make the output voltage of switching power unit rise.

On the other hand, in steady shape work, if feedback end T2 and the resistance between the negative power line 2 at integrated circuit 38 keep high, for example, when the operation of switching power unit is in non-loaded state and makes that the output voltage of switching power unit increases, along with stablizing of output voltage, even stop to provide electric current at signal level checker circuit 15, by the diode 107 in the integrated circuit 38, the voltage that the voltage dividing potential drop that resistor 108 and resistor 39a (see figure 4) are formed is produced can not drop to the lower limit of OSC 106 oscillator signals, so, very inconvenient, just can not so control at the voltage of feedback end T2 and to reduce output voltage.

In order to overcome this unfavorable factor, when switching power unit starts, increase along with the charging voltage of capacitor 33, instantaneous before electric current begins to flow through phototransistor 20b, signal level checker circuit 15 is connecting resistor 39b in addition, feasible feedback end T2 that reduces at integrated circuit 38 and the resistance between the negative power line 2.

As discussed above, switching power unit is carried out the pulse strobe switch operation in light load operation.This helps to reduce the power consumption in light load operation.

As discussed above, in switching power unit, output voltage trends towards increasing in light load operation.In order to proofread and correct it, the current values that flows through phototransistor 20b also increases.This electric current that flows through phototransistor 20b makes it to flow through current sensing resistor 34, and the reference voltage that is provided in the voltage drop of this current sensing resistor 34 and the signal level checker circuit 15 is compared, and when the voltage drop of current sensing resistor 34 was higher than reference voltage, signal level checker circuit 15 was just to soft start capacitor side controller circuit 37 feed-in supplying electric currents and stop to provide electric current to the feedback end T2 of integrated circuit 38.

When detecting supplying electric current, the voltage step-down of the soft start capacitor end T8 that the switch that soft start capacitor side controller circuit 37 is opened to be provided makes at integrated circuit 38.When the voltage step-down at soft start capacitor end T8, arithmetic control circuit 102 is closed the output of 5V voltage adjuster 103, and stops pull-up current being provided and stopping to provide OSC 106 and the working power of pulse-width modulation logical circuit 105 to feedback end T2.

In addition, arithmetic control circuit 102 is to output buffer 101 feed-in disable signal, to stop the work of output buffer 101.This can stop the output T5 feed-in main switching device 5 of drive signal from integrated circuit 38, and thereby switching power unit shutdown switch operation.

Therefore, along with the voltage between

output line

25 and 26 descends, the voltage that is produced by the voltage dividing potential drop of

resistor

23 and 24 also descends, so flowing through the electric current of shunting adjuster 22, photodiode 20a and phototransistor 20b also descends, thereby the voltage drop of current sensing resistor 34 also descends, signal level checker circuit 15 is compared the voltage drop of current sensing resistor 34 with the reference voltage that is provided subsequently, and the voltage of judgement current sensing resistor 34 is reduced to low.So signal level checker circuit 15 is just to the feedback end T2 of integrated circuit 38 feed-in supplying electric current, and stop to provide electric current to soft start capacitor side controller circuit 37.

Therefore, the switch that soft start capacitor side controller circuit 37 closers are provided, the voltage of the soft start capacitor end T8 that makes at integrated circuit 38 uprises.So arithmetic control circuit 102 is opened 5V voltage adjuster 103, and restarts pull-up current to be provided and to provide working power to OSC 106 and pulse-width modulation logical circuit 105 to feedback end T2.In addition, arithmetic control circuit 102 is to output buffer 101 feed-in enable signals, to restart the work of output buffer 101.

This just restarts to provide drive signal from integrated circuit 38 output T5 to main switching device 5, and switching power unit restarts switching manipulation.

Afterwards, when the voltage between

output line

25 and 26 increases once more, just stopped switching manipulation, as discussed above.Yet when the voltage between

output line

25 and 26 descended, the voltage drop of current sensing resistor 34 descended, and restarts switching manipulation, as discussed above.By the repetition of these operations, just can obtain the operation of pulse strobe switch.

In this pulse strobe switch state, increase along with the switching power unit output voltage, this time started from no longer reaching the level of the reference voltage that is provided when the voltage level of current sensing resistor in signal level Correction circuit 15 in the cycle of switching manipulation.This is the beginning of continuous switching mode.

Adopt the technology of above-mentioned the 4th embodiment that discusses just might on by simple practical basis, realize the present invention to the more additional adjunct circuits of commercial pulse width modulation controlled integrated circuit, for example, the production code member that adopts Fuji electronics corporation to produce is integrated circuit or its equivalent integrated circuit of FA 5511.

In the switching power unit of this embodiment, the soft start capacitor side controller circuit 37 that signal level checker circuit 15 is provided in integrated circuit 38 by the repetition opening and closing obtains pulse strobe switch control, and wherein integrated circuit 38 is provided working power and is used as on-off controller.In addition, in pulse strobe switch control, when the switching manipulation of main switching device 5 has stopped, also stopped partly providing working power to integrated circuit 38 main circuits.The power loss that this helps to reduce when switching manipulation stops and being born, and the power consumption that helps to reduce device integral body.

Here, the main circuit of integrated circuit 38 partly comprises: OSC 106, pulse-width modulation logical circuit 105, feedback end T2, and output buffer 101.

In addition, start Correction circuit 35 and so work, when switching power unit when startup work enters into steady state operation, resistor 39b and resistor 39a are being connected in parallel, with the feedback end T2 that reduces at integrated circuit 38 and the resistance between the negative power line 2.This has reduced the current potential of feedback end T2, thereby has guaranteed that switching power unit can carry out the control of reliable output voltage stabilization when the work of stable state.

The 5th embodiment

Fig. 9 is the circuit diagram of the switching power unit of fifth embodiment of the invention.In Fig. 9, all adopt identical reference number to identify with this class circuit element similar among Fig. 4, and no longer repeat explanation them.In the switching power unit of the 5th embodiment, shown signal level Correction circuit 15 in detail, start Correction circuit 35, and the structure of soft start capacitor side controller circuit 37.

Signal level Correction circuit 15 be by

PNP transistor

47 and 48 and

resistor

49,50 and 51 form.Starting Correction circuit 35 is by Zener diode 5, resistor 55,56 and 39b, and NPN transistor 57 is formed.Soft start capacitor side controller circuit 37 is made up of NPN transistor 53 and resistor 52.In the following discussion, PNP transistor and NPN transistor all abbreviate transistor as.

In signal level checker circuit 15, the emitter of the emitter of transistor 47 and transistor 48 links together, and has connected resistor 49 between these emitters and capacitor 33.The base stage of transistor 47 is connecting the node between phototransistor 20b and current sensing resistor 34.

The base stage of transistor 48 is connecting by adopting resistors in

series

50 and 51 to come the node of the reference voltage that voltage produced of voltage-dividing capacitor 33.The collector electrode of transistor 47 is connecting the feedback end of integrated circuit 38 (that is, FA 5511), and the base stage of the transistor 53 that is provided in soft start capacitor side controller circuit 37 is being provided the collector electrode of transistor 48.

As structure discussed above, when switching power unit during with steady state operation, signal level checker circuit 15 is worked in the following manner.

As discussed above, the charging voltage of capacitor 33 is stabilized, and the voltage that adopts

resistor

50 and 51 dividing potential drop charging voltages to be produced uses as reference voltage.This reference voltage is referred to as Eb.On the node between phototransistor 20b and the current sensing resistor 34, the voltage that the signal level of the feedback signal exported with output voltage detector circuit 9 is directly proportional substantially will appear.When this voltage was lower than reference voltage Eb, then transistor 47 was with regard to conducting and transistor 48 just ends.So the electric current I that flows through transistor 47 collector electrodes can be obtained by following formula:

Ia＝(Ea-Ee-Va)/Rd (1)

In above-mentioned formula (1), Ea represents the charging voltage of capacitor 33, Ee is illustrated between phototransistor 20b and the current sensing resistor 34 voltage on the node (promptly, the base voltage of transistor 47), Va is illustrated in the base stage of transistor 47 and the forward voltage between the emitter, and Rd represents the resistance of resistor 49.

Therefore, along with the electric current that flows through phototransistor 20b increases, the electric current that offers the feedback end T2 of integrated circuit 38 will reduce, and, reducing along with flowing through phototransistor 20b, the electric current that then offers the feedback end T2 of integrated circuit 38 will increase.In addition, when the electric current that flows through phototransistor 20b further increases, then voltage will become and is higher than reference voltage Eb on the node between phototransistor 20b and the current sensing resistor 34.This just makes transistor 47 end and transistor 48 conductings, so, will offer soft start capacitor side controller circuit 37 from the electric current of transistor 48 collector electrodes.

Then, soft start capacitor side controller circuit 37 will be discussed.The collector electrode of transistor 53 is connecting the soft start capacitor end T8 of integrated circuit 38 (that is, FA 5511), and emitter is connecting negative power line 2, and base stage is connecting the output of signal level checker circuit 15.

Therefore, when the electric current that provides from signal level checker circuit 15, transistor 53 is with regard to conducting, thereby makes the voltage step-down of soft start capacitor end T8 of integrated circuit 38.

Diode 58 is connected between the soft start capacitor end T8 and capacitor 41 of integrated circuit 38, and this diode 58 is used to the fluctuation of the voltage level of the soft start capacitor end T8 that accelerates at integrated circuit 38, thereby and accelerates oscillatory regime in the pulse gate operation and the switch speed between the inactive state.

If do not insert this diode 58, that is, the soft start capacitor end T8 of integrated circuit 38 is directly connecting capacitor 41, and when transistor 53 conductings, before the charge consumption that capacitor 41 is accumulated, the voltage of soft start capacitor end T8 just can not step-down.This has just postponed stopping of switching manipulation.On the other hand, when transistor 53 ended, the electric current that just needs the time to make arithmetic control circuit provide can charge to capacitor 41 the lower voltage limit level that is higher than OSC 106 oscillator signals.This has just postponed restarting of switching manipulation.Consequently, such situation can take place, in the pulse strobe switch operation, in the cycle of not carrying out switching manipulation, when the load current of switching power unit increases suddenly, the amount that output voltage can descend and be increased.

Can ignore switching manipulation stop and restarting in the application of late effect in, just there is no need to insert diode 58.

Then, startup Correction circuit 35 is discussed.In starting Correction circuit 35, the predetermined voltage that the Zener voltage of Zener diode 54 is hereinafter to be mentioned, this predetermined voltage are to increase to according to the charging voltage at capacitor 33 to be higher than Zener voltage transistor 57 conductings are provided with.Therefore, be higher than Zener voltage (predetermined voltage) when the charging voltage of capacitor 33 increases to, transistor 57 is to be provided by the base current of capacitor 33 by Zener diode 54 and resistor 55.This makes transistor 57 conductings, this transistor 57 that resistor 39b and resistor 39a are connected in parallel, thereby and is reduced in the voltage of the feedback end T2 of integrated circuit 38.

In the switching power unit of this embodiment, signal level Correction circuit 15 obtains pulse strobe switch control by the opening and closing of the soft start capacitor side controller circuit 37 that repeats integrated circuit 38 in the line and provided, and this integrated circuit 38 uses as on-off controller and has been provided working power.In addition, in pulse strobe switch control, in the switching manipulation that stops main switching device 5, also stopped offering integrated circuit 38 main circuit parts, that is, OSC 106, pulse-width modulation logical circuit 105, the working power of feedback end T2 and output buffer 101.This helps to reduce the power loss of being born in the shutdown switch operation, and also helps to reduce the power consumption of device integral body.

In addition, start Correction circuit 35 and so work, make that at switching power unit from start-up operation during to the steady state operation transition, resistor 39b and resistor 39a are connected in parallel, with the feedback end T2 that reduces at integrated circuit 38 and the resistance between the negative power line 2.This has just reduced the current potential at feedback end T2, thereby and guarantees that switching power unit can carry out the control of reliable output voltage stabilization in stable state.

In addition, signal level checker circuit 15 starts Correction circuit 35 and soft start capacitor side controller circuit 37 and can adopt simple circuit structure to realize, and the on-off controller circuit can adopt integrated circuit 38, and for example, FA 5511 realizes.This helps to reduce the size of circuit board, thereby and reduces the volume and the cost of switching power unit.

In addition, on-off controller circuit (integrated circuit 38) can be separated with the main device 5 that goes into operation, and therefore, compare with the situation that other element is integrated in (on single wafer) in the single encapsulation with main switching device and on-off controller circuit, just might adopt main switching device with low on-resistance.This helps to prevent the decline of the power conversion efficiency in the heavy duty operation.By the way, adopt current technology, the main switching device made from other element in single encapsulation can produce the main switching device with high conducting resistance.

The 6th embodiment

Figure 10 is the circuit diagram of the switching power unit of sixth embodiment of the invention.In Figure 10, all adopt identical reference number to identify with this class circuit element similar among Fig. 9, and no longer repeat explanation them.

In the switching power unit of previous embodiment shown in Figure 9, in the pulse strobe switch operation, the cycle of shutdown switch operation and the cycle of carrying out switching manipulation, as discussed above, it depends on the delay in the performed control of output voltage control system.On the contrary, in the switching power unit of present embodiment shown in Figure 10, the comparison reference power source that is provided in signal level Correction circuit 15a can and be carried out between cycle of switching manipulation in cycle of shutdown switch operation and change, thereby, can prolong and adjust the cycle of shutdown switch operation and the cycle of carrying out switching manipulation according to the scope how variation is set.

In this embodiment, in order to allow the setting of this comparison reference power source, in voltage branch circuit that signal level Correction circuit 15 shown in Figure 9 is provided and the

resistor

50 and 51 that is connected in series, resistor 51 is divided into resistor 51a and the 51b among the signal level Correction circuit 15a shown in Figure 10.Node between

resistor

51a and 51b is connected to the soft start capacitor end T8 of integrated circuit 38 by diode 59.

In Figure 10, when switching power unit during with steady state operation, carrying out in the cycle of switching manipulation, be height at the voltage of the soft start capacitor end T8 of integrated circuit 38, and diode 59 prevents that electric current from flowing into node between resistor 51a and the 51b from soft start capacitor end T8.So the base voltage of transistor 48 (that is, comparing reference power source) Esa can be provided by following formula (2) roughly:

Esa＝[(Ra+Rb)×Ec]/(Ro+Ra+Rb) (2)

In above-mentioned formula (2), Ra represents the resistance of resistor 51a, and Rb represents the resistance of resistor 51b, and Ro represents the resistance of resistor 50, and Ec represents the charging voltage of capacitor 33.

On the other hand, when switching power unit was carried out the pulse strobe switch operation, in the cycle of shutdown switch operation, transistor 51 was conductings, and resistor 51b is short circuit.So the base voltage of transistor 48 (that is, comparing reference power source) Esb can be provided by following formula roughly:

Esb＝(Ra×Ec)/(Ro+Ra) (3)

In the formula, keep the relation of Esa＞Esb.By resistor 50 approximately is set, the resistance of 51a and 51b just might freely be provided with the numerical value of Esa-Esb.

When switching power unit is carried out switching manipulation, when output voltage increases owing to for example load current reduces, so increasing to, the base voltage of transistor 47 is higher than voltage Esa, as discussed above, offer the base stage of transistor 53 from the electric current of transistor 48 outputs, this just makes transistor 53 conductings, and therefore also shutdown switch operation of switching power unit.

Consequently, the output voltage of switching power unit begins to descend, and, when the base voltage of transistor 47 drops to when being lower than voltage Esb, then transistor 48 by and make the voltage of soft start capacitor end T8 of integrated circuit 38 become to be height.So switching power unit restarts switch work.As a result, the output voltage of switching power unit increases, and, when increasing to, the base voltage of transistor 47 is higher than voltage Esa, and then switching power unit is with regard to shutdown switch work.Repeat this sequence of operation.

Therefore, adopt the switching power unit of signal level checker circuit 15a as shown in figure 10 to have following described operating characteristic.

In signal level checker circuit 15 shown in Figure 9, relatively the voltage of reference power source is fixed.So, in the switching power unit that adopts this signal level checker circuit 15, when device is carried out the pulse strobe switch operation, carry out the lag characteristic that the switch periods and the length in shutdown switch cycle depend on the performed control of output voltage control system.On the contrary, in adopting the switching power unit of signal level checker circuit 15a as shown in figure 10, carry out the switch periods and the length in shutdown switch cycle and all be longer than the execution switch periods and the length in shutdown switch cycle in the switching power unit that adopts signal level checker circuit 15.In addition, these length can freely be provided with by the numerical value that Esa-Esb suitably is set, as discussed above.

In addition, in adopting the switching power unit of signal level checker circuit 15 as shown in Figure 9, when device was carried out the pulse strobe switch operation, the width (ripple in the output voltage) of set output voltage fluctuation was set as the determined greatest measure of control lag characteristic that equals by the output voltage control system.On the contrary, in adopting the switching power unit of signal level checker circuit 15a as shown in figure 10, the width of output voltage fluctuation is greater than the width of the output voltage fluctuation in the switching power unit that adopts signal level checker circuit 15, in addition, this width can freely be provided with by the numerical value that Esa-Esb suitably is set, as discussed above.

Increase width (that is the ripple of output voltage) that output voltage changes and can produce the advantage that reduces the power loss of in the pulse strobe switch operation, being born by the way down.

Particularly, in the switching power unit that adopts signal level checker circuit 15, switching manipulation originates in the state of shutdown switch operation, and the signal level of feedback signal has only slightly and reduces.On the time point of beginning switching manipulation, the voltage of the feedback end T2 of integrated circuit 38 increases slightly, and therefore, the duty ratio of the drive signal of the output T5 of integrated circuit 38 output is very little (that is, high level period is short) just.

On the contrary, in the switching power unit that adopts signal level checker circuit 15a, before entering the shutdown switch mode of operation, do not begin switching manipulation, the signal level of feedback signal drops to the level of voltage Esb.So.On the time point of beginning switching manipulation, the voltage of the feedback end T2 of integrated circuit 38 increases greatly, and therefore, the duty ratio of the drive signal of the output T5 of integrated circuit 38 output is very big (that is, high level period is long) just.

Therefore, on the time point of beginning switching manipulation, each cycle all can feed out very large electric current by diode 7 from the secondary coil 6 of transformer 3, so, when observing, just in a less time, carry out switch with long time span.This just helps to reduce the loss of power.

Therefore, adopting the pulse strobe switch mode of operation to allow output voltage to exist in the application of less fluctuation width, adopt signal level checker circuit 15 shown in Figure 9, and, reducing power consumption is in the preferential application, adopts signal level checker circuit 15a shown in Figure 10.Under the situation that adopts signal level checker circuit 15a, as discussed above, the width of output voltage fluctuation can be arranged on the fluctuation that produced less than the requirement of using and make simultaneously on the optimal values of power consumption minimum.

By the way down, when the switching power unit that adopts signal level checker circuit 15a was worked with the heavy duty state, its output voltage trended towards reducing.This just makes the base voltage of transistor 47 can be lower than voltage Esa, so switching power unit can be carried out continuous switch.

In the switching power unit of present embodiment, signal level checker circuit 15a obtains pulse strobe switch control by the soft start capacitor side controller circuit 37 that repetition opening and closing integrated circuit 38 is provided in the line, wherein integrated circuit 38 uses as on-off controller, has been provided working power.In addition, in pulse strobe switch control, in the operation of main switching device 5 shutdown switches, also stop to provide working power to integrated circuit 38.This helps to reduce the power loss of being born in the shutdown switch operation, so help to reduce the power consumption of device integral body.

In addition, operation start Correction circuit 35 makes switching power unit enter into the operation of stable state from start-up operation, and resistor 39a and resistor 39b are connected in parallel to reduce to make the feedback end T2 of integrated circuit 38 and the resistance between the negative power line 2.This has just reduced the current potential of feedback end T2, thereby has guaranteed that switching power unit can carry out the control of reliable output voltage stabilization when steady state operation.

In addition, signal level checker circuit 15a starts Correction circuit 35 and soft start capacitor side controller circuit 37 and can adopt simple circuit structure to realize, and the on-off controller circuit can adopt integrated circuit 38, and for example, FA 5511 realizes.This helps to reduce the size of circuit board, thereby and reduces the volume and the cost of switching power unit.

In addition, on-off controller circuit (integrated circuit 38) can be separated with main switching device 5, and therefore, compare with the situation that other element is integrated in (on single wafer) in the single encapsulation with main switching device and on-off controller circuit, just might adopt main switching device with low on-resistance.This helps to prevent the decline of the power conversion efficiency in the heavy duty operation.By the way, adopt current technology, the main switching device made from other element in single encapsulation can produce the main switching device with high conducting resistance.

The 7th embodiment

Figure 11 is the circuit diagram of the switching power unit of seventh embodiment of the invention.In Figure 11, all adopt identical reference number to identify with this class circuit element similar among Fig. 4, and no longer repeat explanation them.

In switching power unit shown in Figure 4, feedback signal be from phototransistor 20b by signal level checker circuit 15, and through to signal level aforesaid after anti-phase increase or reduce after, the feedback end T2 of feed-in integrated circuit 38.On the contrary, in switching power unit shown in Figure 11, feedback signal is from the feedback end T2 of phototransistor 20b by resistor 34 and current regulator circuits 60 feed-in integrated circuits 38.In addition, in the present embodiment, can omit the startup Correction circuit for following reason.

Current correction device circuit 60 can absorb the electric current that is proportional to the voltage of node between phototransistor 20b and resistor 34 from the feedback end T2 of integrated circuit 38.Therefore, when the output voltage of switching power unit when for example being higher than predetermined value, output voltage detector circuit 9 just is increased in the voltage of node between phototransistor 20b and the resistor 34, and current regulator circuits 60 just can absorb electric current from the feedback end T2 of integrated circuit 38 to increase it corresponding to the mode that increases voltage.This just makes in the voltage decline of feedback end T2.

Along with the decline of this voltage, pulse-width modulation logical circuit 105 (see figure 6)s that provided in integrated circuit 38 are passed through the output T5 of integrated circuit 38 to the short drive signal of main switching device 5 feed-in high level period.This makes the secondary coil 6 of transformer 3 descend by the electric current that diode 7 is provided, so can descend with regard to control output voltage.

On the other hand, when the output voltage of switching power unit when for example being lower than predetermined value, output voltage detector circuit 9 just is reduced in the voltage of node between phototransistor 20b and the resistor 34, and current regulator circuits 60 just can absorb electric current from the feedback end T2 of integrated circuit 38 to reduce it corresponding to the mode that reduces voltage.This just makes in the voltage increase of feedback end T2.

Along with the increase of this voltage, pulse-width modulation logical circuit 105 (see figure 6)s that provided in integrated circuit 38 are passed through the output T5 of integrated circuit 38 to the long drive signal of main switching device 5 feed-in high level period.This makes the secondary coil 6 of transformer 3 increase by the electric current that diode 7 is provided, so can increase with regard to control output voltage.

The principle that switching power unit shown in Figure 11 obtains pulse strobe switch control is to be same as the principle that switching power unit shown in Figure 4 obtains pulse strobe switch control.

The switching power unit of present embodiment when starting, starts with the same way as of the common circuit (see figure 5) that adopts FA 5511 (integrated circuit 38).This just might omit the above-mentioned startup Correction circuit of discussing.

Particularly, at time point t1 shown in Figure 7, the charging voltage of capacitor 33 is zero, and the voltage on node between phototransistor 20b and the resistor 34 also is zero, and current correction device circuit 60 does not absorb the electric current from the feedback end T2 of integrated circuit 38.Therefore, be same as the level of 5V voltage adjuster 103 (see figure 6) output voltages at the level of the voltage of feedback end T2.

After this, the charging voltage of the output voltage of switching power unit and capacitor 33 increases, and at time point t3, the output voltage of switching power unit reaches and approaches by

resistor

23 and 24 set predetermined voltages, and electric current flows through phototransistor 20b.This just makes the voltage of between phototransistor 20b and resistor 34 node increase, and begins to reduce at the voltage of the feedback end T2 of integrated circuit 38.Now, just begun to be used to export the control of steady shape voltage.In the cycle of time point t3, the duty ratio of integrated circuit 38 output T5 output drive signals is to be controlled by the voltage level of soft start capacitor end T8.

The above-mentioned operation of discussing is same as common circuit performed operation when starting of adopting FA 5511, and is similar to the discussion in conjunction with switching power unit shown in Figure 4.Switching power unit shown in Figure 11 does not need to start correcting circuit.

As discussed above, switching power unit shown in Figure 11 does not need to start correcting circuit, so it has simple circuit configuration.Yet, in switching power unit,, all can change with temperature such as the characteristic of each element of employed semiconductor device in current correction device circuit 60 as what discussed below with reference to the 8th embodiment.When more disadvantageously, this carries out switch change to normal switch continuously from pulse strobe switch and the desired value of load current is changed when switch change is carried out switch to pulse strobe switch from normal continuously.Therefore, switching power unit shown in Figure 11 is applicable to the application that allows the load current desired value to change.

In the switching power unit of present embodiment, signal level checker circuit 15a obtains pulse strobe switch control by repeating opening and closing soft start capacitor side controller circuit 37.In addition, in pulse strobe switch control, in the operation of main switching device 5 shutdown switches, also stop the main element to integrated circuit 38, that is, OSC 106, pulse-width modulation logical circuit 105, and feedback end T2 and output buffer 101 provide working power.This helps to reduce the power loss of being born in the shutdown switch operation, so help to reduce the power consumption of device integral body.

In addition, when switching power unit starts, current regulator circuits 60 work, the feasible electric current that is adjusted at the feedback end T2 of integrated circuit 38.So the pulse width modulation controlled integrated circuit makes main switching device carry out the switching manipulation with big conducting state duty ratio.This helps time of reducing to start.

In addition, on-off controller circuit (integrated circuit 38) can be separated with main switching device 5, and therefore, compare with the situation that other element is integrated in (on single wafer) in the single encapsulation with main switching device and on-off controller circuit, just might adopt main switching device with low on-state resistance.This helps to prevent the decline of the power conversion efficiency in the heavy duty operation.

The 8th embodiment

Figure 12 is the circuit diagram of the switching power unit of eighth embodiment of the invention.In Figure 12, all adopt identical reference number to identify with this class circuit element similar among Figure 10 and Figure 11, and no longer repeat explanation them.

In Figure 12, current regulator circuits 60 comprises transistor 70 and resistor 72.The collector electrode of transistor 70 is connecting the feedback end T2 of integrated circuit 38, and base stage is connecting the node between resistor 34 and resistor 71, and emitter is connecting negative power line 2 by resistor 72.

When switching power unit is carried out normal switching manipulation continuously, the voltage Ef of the feedback end T2 of integrated circuit 38 can be rough determine by following formula (4).

Ef＝Er-(Ea-Vb)×Re/Rc-Vf (4)

In formula (4), Er is illustrated in integrated circuit 38 (promptly, the output voltage of 5V voltage adjuster 103 (see figure 6)s that provided FA5511), Ea is illustrated in the voltage of node between resistor 71 and the resistor 34, Vb is illustrated in the base stage of transistor 70 and the forward voltage between the emitter, the resistance (see figure 6) of the pullup resistor 108 that is provided in the integrated circuit 38 is provided Re, Rd represents the resistance of resistor 72, and the forward drop of diode 107 (see figure 6)s that provided in the integrated circuit 38 is provided Vf.

Can be clearly seen that from above-mentioned formula (4) voltage Ef is relevant with the forward voltage between the emitter with the base stage of transistor 70.In general, change with temperature during the forward voltage between transistor base and the emitter.Therefore, even under transistor 47 base voltages are stable situation, along with the variation of operating ambient temperature, the forward voltage of transistor 70 also changes, and therefore the voltage at the feedback end T2 of integrated circuit 38 also can change.

In addition, when switching power unit was carried out continuous switch, as discussed above, the voltage level of the feedback end T2 of integrated circuit 38 changed according to the variation of the output voltage of switching power unit, makes output voltage be stabilized.This means: because output voltage depends on the variation of load, so the voltage level that changes feedback end T2 by the variation according to load current comes regulated output voltage.So, represent the load current of switching power unit at the magnitude of voltage of feedback end T2.

In switching power unit, as discussed above, in continuous switching manipulation, along with load current reduces greatly, the base voltage of transistor 47 increases, and, when it becomes the base voltage (comparison reference voltage) that is higher than transistor 48, transistor 53 conductings are to obtain to enter the pulse strobe switch operation.So, if change the voltage of the feedback end T2 of integrated circuit 38 on the time point of this switch according to the operating ambient temperature of switching power unit, then will be very unfavorable, also change according to the operating ambient temperature of switching power unit at the load current of putting this switching time.

According to the application type of connection switching power unit, this application can need the same accurate numerical value with reference value, and this reference value is relevant by estimating that load current determines whether to carry out switch with it.So in this class was used, switching power unit was not very stable.Yet in not needing so accurate application, the switching power unit with suitable simple structure can be suitable for.

By the way down, in Fig. 4, Fig. 9 of above-mentioned discussion and circuit shown in Figure 10, replace the current regulator circuits 60 that is provided, can eliminate the reason that load current changes.This feasible load current that might estimate when mode of operation is switched more accurately.Yet, additional provide start Correction circuit 35 make this circuit structure complicated a little,

In the switching power unit of present embodiment, signal level checker circuit 15 obtains pulse strobe switch control by the soft start capacitor side controller circuit 37 that repeats to be provided in the opening and closing integrated circuit 38, integrated circuit 38 has been provided working power as on-off controller work.In addition, in pulse strobe switch control, in the operation of main switching device 5 shutdown switches, also stop the main circuit part to integrated circuit 38, that is, OSC 106, pulse-width modulation logical circuit 105, feedback end T2 and output buffer 101 provide working power.This helps to reduce the power loss of being born in the shutdown switch operation, so help to reduce the power consumption of device integral body.

In addition, when switching power unit started, current regulator circuits 60 work were with the electric current on the feedback end T2 that is adjusted at integrated circuit 38.So the pulse width modulation controlled integrated circuit makes main switching device to carry out switching manipulation with big conducting state duty ratio.This helps to reduce start-up time.

In addition, signal level checker circuit 15, current regulator circuits 60, and soft start capacitor side controller circuit 37 can realize with simple circuit configuration, and on-off controller circuit mouth can adopt integrated circuit 38, that is and, FA 5511 realizes.This helps to reduce the size of circuit board, thereby and reduces the volume and the cost of switching power unit.

In addition, on-off controller circuit (integrated circuit 38) can be separated with the main device 5 that goes into operation, and therefore, compare with the situation that other element is integrated in (on single wafer) in the single encapsulation with main switching device and on-off controller circuit, just might adopt main switching device with low on-state resistance.This helps to prevent the decline of the power conversion efficiency in the heavy duty operation.

The 9th embodiment

Figure 13 is the circuit diagram of the switching power unit of ninth embodiment of the invention.In Figure 13, all adopt identical reference number to identify with this class circuit element similar among Figure 12, and no longer repeat explanation them.

Circuit shown in Figure 13 is different from circuit shown in Figure 12, and in this circuit, the transistor 77 that has identical characteristics with transistor 70 also is connected in series with resistor 71 in addition.By the effect of transistor 77, circuit shown in Figure 13 can alleviate characteristic with variation of temperature.Particularly, for example, when the operating ambient temperature of switching power unit rose, when the forward voltage between the basic emitter-base bandgap grading of transistor 70 reduced, the forward voltage between transistor 77 base stages and the emitter also reduced.This makes the base voltage of transistor 70 reduce, thereby and has suppressed the change in voltage of the feedback end T2 of integrated circuit 38.

In the switching power unit of present embodiment, signal level checker circuit 15 obtains pulse strobe switch control by the soft start capacitor side controller circuit 37 that repeats to be provided in the opening and closing integrated circuit 38, integrated circuit 38 has been provided working power as on-off controller work.In addition, in pulse strobe switch control, in the operation of main switching device 5 shutdown switches, also stop to provide the working power of integrated circuit 38.This helps to reduce the power loss of being born in the shutdown switch operation, so help to reduce the power consumption of device integral body.

The tenth embodiment

Figure 14 is the circuit diagram of the switching power unit of tenth embodiment of the invention.In Figure 14, all adopt identical reference number to identify with this class circuit element similar among Figure 11, and no longer repeat explanation them.

Circuit shown in Figure 14 is different from circuit shown in Figure 11, and in this circuit, capacitor 75 also is connected between the end T7 and feedback end T2 of integrated circuit 38.In addition, in circuit shown in Figure 14, be mainly used in the phase compensation in the continuous on off state of output stabilizing control system, the series circuit that is made of resistor 73 and capacitor 74 also is connected between the feedback end T2 and negative power line 2 of integrated circuit 38.

Yet, capacitor 74 that is increased and resistor 73, pulse gate flow through produced in the operation below undesirable phenomenon.

When switching power unit was carried out the pulse strobe switch operation, in the cycle of shutdown switch operation, as discussed above, the output voltage of 5V voltage adjuster 103 (see figure 6)s was zero, so the voltage on the feedback end T2 of integrated circuit 38 just descends.Therefore, as discussed above, on the time point of beginning switching manipulation, the output voltage of 5V voltage adjuster 103 rises, so electric current flows into capacitor 74 by diode 107 (see figure 6)s and resistor 108 (see figure 6)s.Therefore, make the voltage of feedback end T2 of integrated circuit 38 reach the lower voltage limit level of the output voltage of OSC 106.This has just postponed the beginning of switching manipulation.

For example, when switching power unit is carried out the pulse strobe switch operation, when load current increases suddenly in the cycle of shutdown switch operation, can detect the decline in the output voltage of switching power unit by the decline in the signal level checker circuit 15 detection feedback signals.In this case, though the very fast rising of the output voltage of 5V voltage adjuster 103 (see figure 6)s, but above-mentioned mentioned delay in the beginning switching manipulation is very unfavorable, makes the output voltage of switching power unit further descend in deferring procedure.

That is to say that in the pulse strobe switch operation, when load increased suddenly, the delay in the operation of pulse strobe switch operation control system can increase the output voltage slippage of switching power unit.Therefore, just wish to increase as much as possible the control rate of pulse strobe switch control system.

By the way down, when the output of 5V voltage regulator circuit 103 (see figure 6)s is risen, provide electric current by capacitor 75 to capacitor 74, this might eliminate the operating delay of pulse strobe switch control system.In addition, by making the electric capacity of capacitor 75 greater than the required value of operating delay of eliminating the pulse strobe switch control system, just might obtain with embodiment illustrated in fig. 10 in the same effect that obtained.

Particularly, when capacitor 75 obtains so high electric capacity, in the pulse strobe switch operation, time point in the beginning switching manipulation, the voltage of the feedback end T2 of integrated circuit 38 just becomes and is higher than the numerical value of corresponding feedback signal level, therefore has the output T5 feed-in main switching device 5 of the drive signal of big duty ratio by integrated circuit 38.So in conjunction with the same cause of setting forth embodiment illustrated in fig. 10, switching power unit shown in Figure 14 helps reducing the power loss of being born in the pulse strobe switch operation.

Yet, to compare with switching power unit embodiment illustrated in fig. 10, it is relatively poor how switching power unit embodiment illustrated in fig. 14 reduces the method reliability of power loss in pulse strobe switch operation, because be difficult to determine the electric capacity of building-out condenser 75.That is to say, in switching power unit embodiment illustrated in fig. 14, the added influence of capacitor 75 phase compensation of output voltage stabilization control system, therefore, this structure can be applicable to and adopt building-out condenser 75 to obtain the situation of required phase compensation.

By the way down, the additional of capacitor 75 also goes for Fig. 4, the situation of building-out condenser 74 and resistor 73 in the switching power unit of 16 and 19 illustrated embodiments.

In the switching power unit of present embodiment, signal level checker circuit 15 obtains pulse strobe switch control by the soft start capacitor side controller circuit 37 that repeats to be provided in the opening and closing integrated circuit 38, integrated circuit 38 has been provided working power as on-off controller work.In addition, in pulse strobe switch control, in the operation of main switching device 5 shutdown switches, also stop the main element to integrated circuit 38, that is, OSC 106, pulse-width modulation logical circuit 105, and feedback end T2 and output buffer 101 provide working power.This helps to reduce the power loss of being born in the shutdown switch operation, so help to reduce the power consumption of device integral body.

The 11 embodiment

Figure 15 is the circuit diagram of the switching power unit of eleventh embodiment of the invention.In Figure 15, all adopt identical reference number to identify with this class circuit element similar among Figure 14, and no longer repeat explanation them.

Switching power unit shown in Figure 15 is different from switching power unit shown in Figure 14, in this device, the phase compensating circuit of being formed by capacitor 74 and resistor 73 among Figure 14, replaced by two series circuits among Figure 15, specifically, another circuit that circuit that capacitor 75 and resistor 76 formed and capacitor 78 and resistor 79 are formed, as shown in Figure 15.Can obtain these capacitors 75 and 78 and the electric capacity and the resistance of

resistor

76 and 79 by following formula (5) and (6), this just might eliminate the effect of phase compensating circuit in the pulse strobe switch operation fully and be implemented in desirable phase compensation in the continuous switching manipulation.

Ca×Rm＝Cb×Rn (5)

Ed＝Er×Ca/(Ca+Cb) (6)

In above-mentioned formula (5) and (6), Ca represents the electric capacity of capacitor 75, Cb represents the electric capacity of capacitor 78, Rm represents the resistance of resistor 76, Rn represents the resistance of resistor 79, the output voltage of Er table 5V voltage adjuster 103 (see figure 6)s, and Ed is illustrated in the voltage drop (variation of voltage) that the feedback end T2 of integrated circuit 38 is produced.

More particularly, Eb is illustrated in the voltage drop (variation of voltage) that has been produced when 5V voltage adjuster 103 has stopped its output in the pulse strobe switch operation on the feedback end T2 of integrated circuit 38.For example, in switching power unit embodiment illustrated in fig. 15, stop instantaneous before its output at 5V voltage adjuster 103, current regulator circuits 60 has absorbed the electric current from feedback end T2, the signal level of the feedback signal of this electric current and the feed-in of phototransistor 20b institute is suitable, so the voltage of feedback end T2 just remains on the voltage level suitable with the institute absorption current.Yet as long as 5V voltage adjuster 103 stops its output, the voltage on feedback end T2 just reduces to zero.Ed represents the difference (voltage drop) of this voltage.

In formula (6), if the value that makes the right is greater than Ed, then in the pulse strobe switch operation, time point in the beginning switching manipulation, voltage on feedback end T2 just becomes and is higher than value corresponding to the feedback signal level, so the drive signal with big duty ratio is just passed through the output T5 feed-in main switching device 5 of integrated circuit 38.So in conjunction with the same cause of setting forth embodiment illustrated in fig. 10, switching power unit shown in Figure 15 helps reducing the power loss of being born in the pulse strobe switch operation.

In addition, in switching power unit embodiment illustrated in fig. 15, by following formula (7) and (8) electric capacity of capacitor and the resistance of resistor are set, just might be in continuous switching manipulation, obtain with the series circuit (seeing Figure 14) that only adopts capacitor 74 and resistor 73 to constitute the same phase compensation characteristic when obtaining phase compensation.

Ca×Rm＝Cb×Rn＝cd×Rt (7)

Cd＝Ca+Cb (8)

In above-mentioned formula (7) and (8), Ca represents the electric capacity of capacitor 75, and Cb represents the electric capacity of capacitor 78, Cd represents the electric capacity (seeing Figure 14) of capacitor 74, Rm represents the resistance of resistor 76, and Rn represents the resistance of resistor 79, and Rt represents the resistance of resistor 73.

In the switching power unit of this embodiment, the soft start capacitor side controller circuit 37 that signal level checker circuit 15 is provided in integrated circuit 38 by the repetition opening and closing obtains pulse strobe switch control, wherein integrated circuit 38 has been provided working power, as on-off controller.In addition, in pulse strobe switch control, when the switching manipulation of main switching device 5 has stopped, also stopped providing working power to integrated circuit 38.The power loss that this helps to reduce when switching manipulation stops and being born, and the power consumption that helps to reduce device integral body.

The 12 embodiment

Figure 16 is the circuit diagram of the switching power unit of twelveth embodiment of the invention.In Figure 16, all adopt identical reference number to identify with this class circuit element similar among Fig. 4, and no longer repeat explanation them.

In switching power unit embodiment illustrated in fig. 16, omitted employed auxiliary control source in Fig. 4, and replace adopt diode 31 to come the voltage that rectification respond in the ancillary coil 32 of transformer 3 and the direct current that produces as the power supply use of control circuit, and thereby be direct feed-in capacitor 46.

When switching power unit shown in Figure 16 begins to start, as discussed above, cross signal level checker circuit 15 by the starting current that startup resistor 29 is provided, and the time span that it flows through need satisfy makes the charging voltage of capacitor 46 can reach integrated circuit 38, promptly, FA 5511, the work starting resistor.Here, for fear of this point, provide starting switch device circuit 18 in addition again.

The output current of phototransistor 20b (feedback signal) is by diode 80 FD feed level checker circuit 15, and starting switch device circuit 81 and start Correction circuit 82 by monitoring the voltage on node between phototransistor 20b and the diode 80 confirms whether there is feedback signal.

Pass through the anode feed-in of line 84 by 15 consumed current of signal level checker circuit (this current sinking comprises by comparing reference power source institute consumed current), and the negative terminal of capacitor 46 is provided through line 83 by the switch that is provided in the starting switch device circuit 81 again from capacitor 46.On the other hand, the electric current by phototransistor 20b is from the anode feed-in of capacitor 46, and again by diode 80, current sensing resistor 34 and the switch that is provided in starting switch device circuit 81 turn back to the negative terminal of capacitor 46.

When switching power unit began to start, the internal switch of starting switch device circuit 81 and the internal switch that starts in the Correction circuit 82 were all closed, and the output voltage of switching power unit is lower than predetermined target voltage.So signal level checker circuit 15 (comprise wherein provided comparison reference power source) and phototransistor 20b do not consume any electric current.Therefore, because the starting current by startup resistor 29, the charging voltage of capacitor 46 is accelerated to rise and the work that reaches integrated circuit 38 (that is, FA 5511) begins voltage level.Here, capacitor 46 charging voltages required time of rising is approximately the same short with required time of the ordinary construction of employing FF 5511.

The startup work of switching power unit then, is discussed with reference to signal waveforms shown in Figure 17.

At the time point A0 shown in Figure 17 (a), direct voltage is applied between positive and

negative power line

1 and 2, and the charging current owing to being provided by startup resistor 29 makes the voltage drop 213 of capacitor 46 increase gradually.At time point A1, the voltage drop 213 of capacitor 46 reaches the predetermined work of integrated circuit 38 (that is, FA 5511) and begins voltage, voltage at the in-line power line 104 of integrated circuit 38 inside rises, so OSC 106, pulse-width modulation logical circuit 105 and output buffer 101 are started working.

So OSC 106 will have the oscillator signal 214 feed-in pulse-width modulation logical circuits 105 of constant upper and lower bound and constant cycle, therefore, the voltage 216 on the soft start capacitor end T8 of integrated circuit 38 just increases gradually.

In addition, at time point A1, as discussed above, starting switch 81 ends, and therefore, signal level checker circuit 15 is not provided operating current.So the output current of signal level checker circuit 15 is zero.In addition, the switch that starts Correction circuit 82 ends, so, diode 107 (see figure 6)s that voltage 215 on the feedback end T2 of integrated circuit 38 is provided in equaling by integrated circuit 38, the branch pressure voltage that the voltage dividing potential drop that resistor 108 (see figure 6)s and resistor 39a (seeing Figure 16) constitute is produced.Here, the resistance of resistor 39a can be arranged to that this branch pressure voltage has approximately and the same level of the upper voltage limit level of the oscillator signal 214 of OSC 106.

As discussed above, voltage 216 on the soft start capacitor end T8 of integrated circuit 38 and the voltage 215 on the feedback end T2 voltage level that is lower than or is higher than the oscillator signal 214 of OSC 106 no matter, pulse-width modulation logical circuit 105 all passes through the voltage of output T5 output high level.

Therefore, shown in Figure 17 (c), in time point A0 is during the cycle of time point A2, the level of the voltage 216 on the soft start capacitor end T8 of integrated circuit 38 was lower than in cycle of voltage level of oscillator signal 214 of OSC 106, kept low at the voltage 217 of the output T5 of integrated circuit 38.At time point A2, when level moment of the voltage 216 on the soft start capacitor end T8 of integrated circuit 38 surpasses the voltage level of oscillator signal 214 of OSC 106, then the voltage 217 at the output T5 of integrated circuit 38 becomes height, and in the corresponding cycle, keep high, make main switching device 5 conductings.

When main switching device 5 by this way during conducting, voltage between

output line

25 and 26 will increase a little, and, in the cycle of time point A3, along with the increase of the voltage 216 on the soft start capacitor end T8 of integrated circuit 38, the duty ratio of the drive signal 217 of the output T5 output by integrated circuit 38 continues to increase.This just makes the output voltage of switching power unit to increase fast.

At time point A3, when the output voltage of switching power unit reaches near predeterminated target voltage (promptly, when the voltage that obtains from the voltage dividing potential drop of

resistor

23 and 24 output voltages reaches the level that is approximately equal to the comparison reference voltage in shunting adjuster 22) time, electric current just flows through shunting adjuster 22 and photodiode 20a, and the voltage on node between phototransistor 20b and the diode 80 increases.One when detecting increase in this voltage, and starting switch device circuit 81 makes its internal switch conducting, can flow through signal level checker circuit 15 and resistor 34 to allow electric current.This just makes relevant circuit start working.

On the other hand, because the ancillary coil 32 of transformer 3 provides electric current by diode 31, the moment of the charging voltage of capacitor 46 before time point A3 begins to increase, and at this moment the output voltage of switching power unit reaches predetermined target voltage.At time point A3, the charging voltage of capacitor 46 has reached by the ancillary coil 32 of the predeterminated target output voltage of switching power unit and transformer 3 and the determined numerical value of ratio of winding between the secondary coil 6.So the electric current that flows through signal level checker circuit 15 and resistor 34 can prevent that the operating voltage of integrated circuit 38 from dropping to and be lower than predetermined minimum, thereby prevent its fault.

At time point A3, start Correction circuit 82 and make its internal switch conducting, work as starting switch device circuit 81, and resistor 39b and resistor 39a are connected in parallel.Now, just as will be discussed, the voltage 215 on the feedback end T2 of integrated circuit 38 begins to carry out the work of stable state.It should be noted that Figure 17 has just illustrated the example that switching power unit starts in the heavy duty state, and comprise the example of having discussed shown in Figure 8.

When the current value that flows through phototransistor 20b during less than predetermined value set in signal level checker circuit 15, signal level checker circuit 15 provides electric current to feedback end T2, on the contrary, when the current values that flows through phototransistor 20b during greater than predetermined value set in signal level checker circuit 15, signal level checker circuit 15 is to soft start capacitor side controller circuit 37 feed-in electric currents, make the internal switch conducting of soft start capacitor side controller circuit 37, and stop main circuit part to integrated circuit 38, promptly, OSC 106, pulse-width modulation logical circuit 105, feedback end T2 and output buffer 101 provide working power.

By the way down, signal level checker circuit 15 does not simultaneously provide electric current to feedback end T2 and soft start capacitor side controller circuit 37.

In addition, when the feedback end T2 of integrated circuit 38 provided electric current, the function of signal level checker circuit 15 was to reduce the electric current that is provided and the electric current that increase is provided when the current value that flows through phototransistor 20b reduces when the current value that flows through phototransistor 20b increases at signal level checker circuit 15.This function allows the output voltage of switching power unit can be stabilized on the value of predeterminated target.

By the way down, when switching power unit starts and between switching power unit is during in steady state operation, startup Correction circuit 82 switches in the resistance between feedback end T2 and the negative power line 2.This just guarantees that switching power unit can work reliably.

Particularly, when switching power unit began to start, not work of signal level checker circuit 15 was so signal level checker circuit 15 just can not provide any electric current.Therefore, resistor 39a presents high resistance, make by the diode 107 that is provided in the integrated circuit 38 (being FA 5511), resistor 108 (see figure 6)s, and the resulting voltage of resistor 39a (seeing Figure 16) voltage dividing potential drop approaches the upper limit of the oscillator signal 214 of OSC 106.Situation if not so, even the voltage level on the soft start capacitor end T8 of integrated circuit 38 216 increases, voltage level 215 on feedback end still can keep below the lower limit of the oscillator signal of OSC 106, and pulse-width modulation logical circuit 105 (see figure 6)s are not by output T5 output high level signal.This just makes the output voltage of switching power unit not rise.

On the other hand, in steady state operation, if the resistance between feedback end T2 and negative power line 2 remains height, for example, when the output voltage of switching power unit enters work under the no-load condition along with switching power unit and when increasing, come regulated output voltage as adopting mode discussed above, when even signal level checker circuit 15 stops electric current being provided, but, also can not drop to the lower voltage limit of the oscillator signal that is lower than OSC 106 at the voltage of feedback end T2 owing to the electric current that the output line 104 from 5V voltage adjuster 103 (see figure 6)s is provided by diode 107 and resistor 108.Very inconvenient is that this makes the output voltage of switching power unit not descend.

In order to overcome this inconvenience, when switching power unit started, at time point A3, startup Correction circuit 82 reduced the resistance between feedback end T2 and negative power line 2.After time point A3, the internal switch of starting switch device circuit 81 and startup Correction circuit 82 all keeps conducting, so, in underloaded operation, switching power unit is just carried out the pulse strobe switch operation, and its principle is same as the principle of discussing in conjunction with embodiment illustrated in fig. 4.This helps to reduce the power loss in light load operation.

Switching power unit embodiment illustrated in fig. 16 allows to be omitted in switching power unit shown in Figure 4 and uses capacitor 33 and diode 30, needs additional starting switch device circuit 81 but replace.In this embodiment, starting switch device circuit 81 can easily be included in the integrated circuit, but can not comprise capacitor 33 in integrated circuit.So, this embodiment is applicable to produce and comprises the new integrated circuit of FA 5511 or have and soft start capacitor side controller circuit, signal level checker circuit, starting switch device circuit starts Correction circuit and other adjunct circuit equivalent integrated circuit together.

The influence that this embodiment drifts about than the temperature correlation that is more vulnerable to the forward voltage of diode 80 embodiment illustrated in fig. 4, in the handoff procedure that carries out between pulse strobe switch and the continuous switch, can produce the shortcoming of the little degree temperature correlation drift of load current desired value.Therefore, in the application of the strict elimination of needs temperature correlation drift effect, it is wise adopting embodiment illustrated in fig. 4, and in not needing the application of so being strict with, adopts the circuit of present embodiment just can satisfy.

In the switching power unit of present embodiment, signal level checker circuit 15 obtains pulse strobe switch control by the soft start capacitor side controller circuit 37 that repeats to be provided in the opening and closing integrated circuit 38, integrated circuit 38 has been provided working power as on-off controller work.In addition, in pulse strobe switch control, in the operation of main switching device 5 shutdown switches, also stop the main circuit element to integrated circuit 38, that is, OSC 106, pulse-width modulation logical circuit 105, feedback end T2 and output buffer 101 provide working power.This helps to reduce the power loss of being born in the shutdown switch operation, so, help to reduce the power consumption of device integral body.

In addition, start Correction circuit 35 work, make the second resistor 39b and the first resistor 39a be connected in parallel, with the feedback end T2 that reduces at integrated circuit 38 and the resistance between the negative power line 2.This has just obviously reduced the current potential at feedback end T2, so integrated circuit 38 can make main switching device 5 carry out switching manipulation apace.This helps to reduce start-up time.

In addition, work by starting switch device circuit 81, when switching power unit begins to start, the starting current that is provided by startup resistor 29 can prevent to flow into signal level checker circuit 15, and so and the charging voltage of the capacitor 46 that extended reaches the required time of work starting resistor of integrated circuit 38 (that is, FA 5511).

The 13 embodiment

Figure 18 is the circuit diagram of the switching power unit of thriteenth embodiment of the invention.In Figure 18, all adopt identical reference number to identify with this class circuit element similar among Fig. 9 and Figure 16, and no longer repeat explanation them.

In Figure 18, signal level checker circuit 15 be by

resistor

49,50 and 51 and

transistor

47 and 48 constitute.Soft start capacitor side controller circuit 37 is made of resistor 52 and transistor 53.Starting switch device circuit 81 is made of resistor 85 and transistor 84.Start Correction circuit 82 and be by

resistor

87 and 39b and transistor 86 constitute.

As above-mentioned discuss shown in Figure 17, when switching power unit began to start, at time point A3, electric current began to flow into phototransistor 20b, and the voltage on node between the emitter of phototransistor 20b and the diode 80 increases.This voltage passes through the base stage of resistor 85 feed-in transistors 80 and the base stage of passing through resistor 87 feed-in transistors 86, and makes

transistor

84 and 86 conductings.Because the conducting of transistor 84, current flows through resistor 34 and by

resistor

50 and 51 series circuits that constituted, and this base current begins to flow through transistor 47.So signal level checker circuit 15 is started working.

As discussed above,, there is not current flowing signal level checker circuit 15 to the cycle of time point A3.The charging voltage of this capacitor 46 that can prevent to extend reaches integrated circuit 38 (that is work starting resistor required time FA5511).

In addition, because the result of transistor 86 conductings, resistor 39b is attached between the feedback end T2 and negative power line 2 of integrated circuit 38.This guarantees that switching power unit can carry out the control of reliable output voltage stabilization in steady state operation.

By the way down, to the cycle of time point A3, diode 80 prevents the base current of

transistor

47,84 and 86 along following path flow, and this path comprises, along anode from capacitor 46, to resistor 49, to the emitter of transistor 47, to the base stage of transistor 47, to resistor 85, to the base stage of transistor 84, to the emitter of transistor 84, to negative power line 2, and to the path of the negative terminal of capacitor 46, perhaps along anode, to resistor 49, to the emitter of transistor 47 from capacitor 46, base stage to transistor 47, to resistor 87, to the base stage of transistor 86, to the emitter of transistor 86, to negative power line 2, and to the path of the negative terminal of capacitor 46.So, in this cycle, prevented the conducting of

transistor

47,84 and 86, thereby can prevent the work of signal level checker circuit 15 and prevent that resistor 39a is connected between the feedback end T2 and negative power line 2 of integrated circuit 38.

In the switching power unit of present embodiment, signal level checker circuit 15 obtains pulse strobe switch control by the soft start capacitor side controller circuit 37 that repeats to be provided in the opening and closing integrated circuit 38, integrated circuit 38 has been provided working power as on-off controller work.In addition, in pulse strobe switch control, in the operation of main switching device 5 shutdown switches, also stop the main circuit part to integrated circuit 38, that is, OSC 106, pulse-width modulation logical circuit 105, feedback end T2 and output buffer 101 provide working power.This helps to reduce the power loss of being born in the shutdown switch operation, so, help to reduce the power consumption of device integral body.

In addition, start the operation of correcting circuit 82, make when switching power unit when start-up operation carries out the transition to steady state operation, the second resistance 39b and the first resistance 39a are connected in parallel, with the feedback terminal T2 of minimizing integrated circuit 38 and the resistance between the negative power line 2.Reduced current potential like this, so this has guaranteed that switching power unit can carry out the control of reliable output voltage stabilization when steady state operation at feedback terminal T2.

In addition, operation by starting switch circuit 81, when switching power unit begins to start, prevent to flow through signal level checker circuit 15 by the starting current that starting resistance 29 is provided, and the charging voltage that has therefore prolonged capacitor 46 reaches integrated circuit 38, and (that is, operation FA5111) begins the required time of voltage.

In addition, signal level checker circuit 15, starting switch circuit 81, start correcting circuit 82 and soft start capacitor terminal control unit circuit 37 and can adopt simple circuit configuration to realize, and the on-off controller circuit can adopt integrated circuit 38, (that is, FA5511) realize.Help to reduce the size of circuit board like this, thereby reduce the volume and the cost of switching power unit.

The 14 embodiment

Figure 19 is the circuit diagram of the 14 embodiment switching power unit among the present invention.In Figure 19, all adopt identical reference number to identify with this class circuit element similar among Figure 16, and no longer repeat explanation them.

Switching power unit shown in Figure 19 is different from switching power unit shown in Figure 16, in this device, omitted starting switch device circuit 81 shown in Figure 16, and the feedback line 83 with signal level checker circuit 15 current sinkings of replacing is connected to and starts Correction circuit 82.Observe this device on the relevant position in switching power unit and be same as the voltage waveform of switching power unit shown in Figure 16, and thereby just study difference in operation in following discussion from its voltage waveform of startup until the cycle of steady state operation.

In Figure 17, at time point A3, when starting the internal switch conducting of Correction circuit 82, the operating current of signal level checker circuit 15 flows through the internal switch that starts Correction circuit 82 with the electric current that flows through resistor 34, so signal level checker circuit 15 is started working.In addition, owing to start the internal switch conducting of Correction circuit 82, as discussed above, resistor 39b is connected between the feedback end T2 and negative power line 2 of integrated circuit 38.

During cycle from time point A0 to time point A3, diode 88 can prevent that electric current is along following path flow, this path is from the anode of capacitor 46, to the operating current supply line 89 of signal level checker circuit 15, to signal level checker circuit 15, to resistor 34, to resistor 39b, to resistor 39a, to negative power line 2, to capacitor 46.So in this cycle, diode 88 prevents 15 work of signal level checker circuit.

The switching power unit of present embodiment has than switching power unit embodiment illustrated in fig. 16 simple circuit configuration more.Yet, disadvantageously, the switching power unit of present embodiment more is subject to the influence of the temperature correlation drift of diode 88 forward drops, in addition, has increased the drift of temperature correlation in the load current desired value of carrying out switch between pulse strobe switch and the continuous switch.So this structure is applicable to the negligible application of the effect of temperature drift.

In the switching power unit of this embodiment, the soft start capacitor side controller circuit 37 that signal level checker circuit 15 is provided in integrated circuit 38 by opening and closing obtains pulse strobe switch control, wherein integrated circuit 38 has been provided working power, as on-off controller.In addition, in pulse strobe switch control, when the switching manipulation of main switching device 5 has stopped, also stopped providing working power to integrated circuit 38.The power loss that this helps to reduce when switching manipulation stops and being born, and the power consumption that helps to reduce device integral body.

The 15 embodiment

Figure 20 is the circuit diagram of the 15 embodiment switching power unit among the present invention.In Figure 20, all adopt identical reference number to identify with this class circuit element similar among Figure 18, and no longer repeat explanation them.

As shown in Figure 7, when the startup of switching power unit begins, at time point A3, when electric current began to flow through phototransistor 20b and the voltage of node increases between phototransistor 20b emitter and diode 80, this voltage made transistor 86 conductings by base resistor 87.Because the conducting of transistor 86, current flows through resistor 34 and flow through the series circuit that constitutes by resistor 50 and 51.This makes base current flow through transistor 47, and therefore signal level checker circuit 15 is started working.

In the cycle of time point A3, there is not current flowing signal level checker circuit 15.These capacitor 46 charging voltages that can prevent to extend reach integrated circuit 38, and (that is, work FA5511) begins the required time of voltage.In addition, because the conducting of transistor 86, the series circuit that diode 88 and resistor 39b constitute is attached between the feedback end T2 and negative power line 2 of integrated circuit 38.This has just guaranteed that switching power unit can carry out the control of reliable output voltage stabilization in steady state operation.

By the way down, to the cycle of time point A3, diode 80 prevents that the base current of

transistor

47 and 86 is along following path flow, this path comprises, along anode, to resistor 49, to the emitter of transistor 47 from capacitor 46, base stage to transistor 47, to resistor 87, to the base stage of transistor 86, to the emitter of transistor 86, to negative power line 2, and to the path of the negative terminal of capacitor 46.So in this cycle, diode 80 has prevented the conducting of

transistor

47 and 86, thereby can prevent the work of signal level checker circuit 15 and prevent that resistor 39a is connected between the feedback end T2 and negative power line 2 of integrated circuit 38 by diode 88.

On the other hand, during cycle from time point A0 to time point A3, diode 88 can prevent electric current along following path flow, and this path is from the anode of capacitor 46, to resistor 49, emitter to transistor 47, to the base stage of transistor 47, to resistor 34, to resistor 39b, to resistor 39a, and to capacitor 46 negative terminals.So in this cycle, diode 88 can prevent 15 work of signal level checker circuit.

In the switching power unit of this embodiment, the soft start capacitor side controller circuit 37 that signal level checker circuit 15 is provided in integrated circuit 38 by the repetition opening and closing obtains pulse strobe switch control, wherein integrated circuit 38 is provided sub-working power, as on-off controller.In addition, in pulse strobe switch control, when the switching manipulation of main switching device 5 has stopped, also stop the main circuit part to integrated circuit 38, that is, OSC 106, pulse-width modulation logical circuit 105, feedback end T2 and output buffer 101 provide working power.The power loss that this helps to reduce when switching manipulation stops and being born, and the power consumption that helps to reduce device integral body.

In addition, signal level checker circuit 15 starts correcting circuit 82 and soft start capacitor terminal control unit circuit 37 and can adopt simple circuit configuration to realize, and the on-off controller circuit can adopt integrated circuit 38, (that is FA5511) realization.Help to reduce the size of circuit board like this, thereby reduce the volume and the cost of switching power unit.

The 16 embodiment

Figure 21 is the circuit diagram of the 16 embodiment switching power unit among the present invention.In Figure 21, with Figure 10, this similar class circuit element all adopts identical reference number to identify in 16,18 and 19, and no longer repeats the explanation to them.

At Figure 16, in the switching power unit shown in 18,19 and 20, in the pulse strobe switch operation, the cycle of shutdown switch operation and the cycle of carrying out switching manipulation,, all depend on the delay in the performed control of output voltage control system as discussed above.On the contrary, in the switching power unit shown in Figure 21 of present embodiment, be similar to switching power unit shown in Figure 10, the comparison reference voltage that is provided in signal level checker circuit 15a is to change between the cycle of the cycle of shutdown switch operation and execution switching manipulation, how feasible basis is provided with the width of this variation, can prolong and adjust the cycle of shutdown switch operation and the cycle of carrying out switching manipulation.

Particularly, in this embodiment, in order to obtain corresponding at the power in conjunction with the comparison reference power source of Figure 18 and 20 above-mentioned discussion, in resistor 50 that is connected in series and 51 voltage branch circuits that constituted, electronegative potential resistor 51 on one side is divided into resistor 51a and 51b.Be connected to the collector electrode of the transistor 53 that is provided by diode 59 at the node between resistor 51a and the 51b in soft start capacitor side controller circuit 37, the collector electrode of transistor 53 is connected to the soft start capacitor end T8 of integrated circuit 38 by diode 90.

If do not provide diode 90 (promptly, if the negative electrode of the collector electrode of transistor 53 and diode 59 directly is connected with the soft start capacitor end T8 of integrated circuit 38, wherein do not connect diode 90), when switching power unit begins to start, at starting switch device circuit 81 and the internal switch that starts Correction circuit 82 all is in the cycle of closing, high level voltage from the anode of capacitor 46 by

resistor

50 and 51 and diode 59 be applied to the soft start capacitor end T8 of integrated circuit 38.This has closed the output of integrated circuit 38 by its output T5, so make switching power unit not start.This problem can overcome by diode 90 is provided.

In addition, operation by starting switch circuit 81, when switching power unit begins to start, prevent to flow through signal level checker circuit 15 by the starting current that starting resistance 29 is provided, and the charging voltage that has therefore prolonged capacitor 46 reaches integrated circuit 38, and (that is, work FA5111) begins the required time of voltage.

In addition, level checker circuit, starting switch circuit 81, start correcting circuit 82 and soft start capacitor terminal control unit circuit 37 and can adopt simple circuit configuration to realize, and the on-off controller circuit can adopt integrated circuit 38, (that is, FA5511) realize.Help to reduce the size of circuit board like this, thereby reduce the volume and the cost of switching power unit.

In addition, on-off controller circuit (integrated circuit 38) can be separated with main switching device 5, and therefore, compare with the situation that other element is integrated in (on single wafer) in the single encapsulation with main switching device and on-off controller circuit, just might adopt main switching device with low on-resistance state.This helps to prevent the decline of the power conversion efficiency in the heavy duty operation.

The 17 embodiment

Figure 22 is the circuit diagram of the 17 embodiment switching power unit among the present invention.In Figure 22, all adopt identical reference number to identify with this class circuit element similar among Figure 11 and 16, and no longer repeat explanation them.Switching power unit embodiment illustrated in fig. 22 has been ignored startup Correction circuit 82 shown in Figure 16, and additional providing with current regulator circuits shown in Figure 11 60 as an alternative.

In switching power unit embodiment illustrated in fig. 22, feedback signal is passed through diode 80, resistor 34, and the feedback end T2 of current regulator circuits 60 feed-in integrated circuits 38 from phototransistor 20b.Current regulator circuits 60 is from the electric current of the feedback end T2 of absorption integrated circuit 38, and this electric current is proportional to the voltage of node between diode 80 and resistor 34.

Therefore, when the output voltage of switching power unit for example is higher than predetermined value, output voltage detector circuit 9 is increased in the voltage on the node between diode 80 and the resistor 34, and current regulator circuits 60 increases the electric current that is absorbed from the feedback end T2 of integrated circuit 38 in the mode that increases corresponding to voltage.This just makes the voltage of feedback end T2 reduce.

Along with reducing of this voltage, pulse-width modulation logical circuit 105 (see figure 6)s that provided in integrated circuit 38 are passed through the drive signal feed-in main switching device 5 of the output T5 of integrated circuit 38 with the high level period shortening.This makes the secondary coil 6 of transformer 3 can reduce by the electric current that diode 7 is provided, and the reducing of the output voltage that therefore can control.

On the other hand, when the output voltage of switching power unit for example is lower than predetermined voltage, output voltage detector circuit 9 reduces the voltage of node between diode 80 and resistor 34, current regulator circuits 60 reduces from the electric current of the feedback end T2 absorption of integrated circuit 38 in the mode that reduces corresponding to voltage, and this just makes in the voltage increase of feedback end T2.

Along with the increase of this voltage, pulse-width modulation logical circuit 105 (see figure 6)s that provided in integrated circuit 38 will have the long drive signal feed-in main switching device 5 of high level period by the output T5 of integrated circuit 38.This makes the secondary coil 6 of transformer 3 increase by the electric current that diode 7 is provided, thereby the output voltage of being controlled increases.

When switching power unit begins to start, as discussed above, the starting current that provides by startup resistor 29 flows through signal level checker circuit 15, and the work that these capacitor 46 charging voltages that extended reach integrated circuit 38 (that is, FA 5511) begins the required time of voltage.In order to prevent this phenomenon, the starting switch device circuit 81 that this paper provides in addition.

The output current of phototransistor 20b (feedback signal) is by diode 80 FD feed level checker circuit 15, and starting switch device circuit 81 is by monitoring that the voltage of node determines whether to exist feedback signal between phototransistor 20b and diode 80.

15 consumed current of signal level checker circuit (comprising comparison reference power source institute consumed current) feed out by line 84 from the anode of capacitor 46, and the negative terminal of capacitor 46 is provided by line 83 and the switch that provided in starting switch device circuit 81.On the other hand, the electric current by phototransistor 20b feeds out from the anode of capacitor 46, and by diode 80, current sensing resistor 34 and the switch that is provided in starting switch device circuit 81 turn back to the negative terminal of capacitor 46.

When switching power unit began to start, the internal switch of starting switch device circuit 81 was closed, and the output voltage of switching power unit is lower than predetermined target voltage.So signal level checker circuit 15 (comprise wherein provided comparison reference power source) or phototransistor 20b do not consume any electric current.Therefore, because the starting current by startup resistor 29, the charging voltage of capacitor 46 is accelerated to rise and the work that reaches integrated circuit 38 (that is, FA 5511) begins voltage level.

In addition, when switching power unit started, current regulator circuits 60 work was with the electric current of the feedback end T2 that is adjusted at integrated circuit 38.So the pulse width modulation controlled integrated circuit makes main switching device recently carry out switching manipulation with the duty of big conducting state.This helps to reduce start-up time.

In addition, operation by starting switch device circuit 81, when switching power unit begins to start, the starting current that is provided by startup resistor 29 is prevented from flowing into signal level checker circuit 15, and thereby the work that capacitor 46 charging voltages that extended reach integrated circuit 38 (that is, FA 5511) begins the voltage required time.

In embodiment discussed in this article, the FA that is produced 5511 of Fuji electronics corporation can be used as on-off controller and uses.Yet, also might use any other integrated circuit to realize comparatively simple circuit configuration with equivalent function.

In the switching power unit disclosed in the mentioned unexposed No.H10-304658 of Japanese patent application, start-up circuit need adopt high voltage withstanding control device to cut out by the AC power of commercialization transmission of electricity being carried out rectification and the level and smooth voltage that obtains (in the drain electrode of FET as main switching device) in background technology.Disadvantageously, this has just increased the cost of switching power unit.In order to overcome this shortcoming, start-up circuit has adopted main switching device to be encapsulated in structure in the single encapsulation with other element that comprises control device.Yet, adopt current technology, also can not in same encapsulation, make main switching device with other such element with low on-state resistance.This will reduce the power conversion efficiency that switching power unit is worked in the heavy duty state.

In order to address this problem, in the switching power unit of the embodiment that discusses, on-off controller and main switching device are separated hereinafter.This just might use the main switching device with low on-state resistance, thereby obtains high power conversion efficiency.

As discussed above, according to the present invention, switching power unit adopts the comparative result of output dc voltage and preset reference voltage as feedback signal, and signal level according to feedback signal, drive main switching device, come opening and closing to offer the working power of the main switching device drive system that drives main switching device.So, in pulse strobe switch control, in the operation of main switching device 5 shutdown switches, also stop to provide working power to the main switching device drive system.This helps to reduce the power loss of being born in the shutdown switch operation, so, help to reduce the power consumption of device integral body.

According to the present invention, switching power unit comprises: output dc voltage is compared with preset reference voltage and export the output voltage detector of comparative result as feedback signal; According to the on-off controller that drives and control main switching device from the feedback signal of output voltage detector; Monitor the signal level of feedback signal and be used for the signal level checker of the operating control signal of opening and closing on-off controller according to the signal level output that monitors; And utilize the working power that on-off controller provides and be used for the operation/not operation derailing switch of opening and closing on-off controller according to operating control signal from the signal level checker.So, just can obtain pulse strobe switch and control because the signal level checker repeats the operation/not operation derailing switch of opening and closing by working power that on-off controller provides.In addition, in pulse strobe switch control, in the switching manipulation that stops main switching device, also stop to provide working power to on-off controller.This helps to reduce the power loss of being born in the shutdown switch operation, so, help to reduce the power consumption of device integral body.

According to the present invention, in switching power unit, the signal level of feedback signal is compared with the signal level that oscillator signal produces in advance, and according to result relatively, determine the conducting state duty ratio of the drive signal of feed-in main switching device, and carry out in pulse strobe switch control and the switching between the switch control continuously.In addition, in pulse strobe switch control, in the switching manipulation that stops main switching device, also stop to provide working power to the driving switch device.So, can carry out in pulse strobe switch control and the switching between the switch control continuously with high accuracy.In addition, in pulse strobe switch control, in the switching manipulation that stops main switching device, also stop to provide working power to driving main switching device.This helps to reduce the power loss of being born in the shutdown switch operation, so, help to reduce the power consumption of device integral body.

Claims

1. switching power unit with series circuit, it comprises the primary coil of transformer and is connected main switching device between the positive and negative power line, this positive and negative power line is connecting DC power supply again, and this switching power unit output is carried out direct voltage that rectification obtain to carried out switching manipulation by main switching device at the high frequency voltage of the secondary coil induction of transformer by adopting rectifier;

It is characterized in that, the comparative result of switching power unit use between direct voltage and preset reference voltage is as feedback signal, and driving main switching device, according to the signal level of feedback signal, come opening and closing to offer the working power of the main switching device drive system that drives main switching device.

2. switching power unit with series circuit, it comprises the primary coil of transformer and is connected main switching device between the positive and negative power line, this positive and negative power line is connecting DC power supply again, and this switching power unit output is carried out direct voltage that rectification obtain to carried out switching manipulation by main switching device at the high frequency voltage of the secondary coil induction of transformer by adopting rectifier;

It is characterized in that switching power unit also comprises:

Output voltage detector, it will be compared with preset reference voltage by the direct voltage that rectification obtains, and the result who exports this comparison is as feedback signal;

On-off controller, it drives according to the feedback signal of being exported by output voltage detector and the control main switching device;

The signal level checker, it monitors the signal level of feedback signal and is used for the operating control signal of opening and closing on-off controller according to the signal level output that is monitored; And,

Operation/not operation derailing switch, it is provided in the line, provides working power by this circuit to on-off controller, and comes the opening and closing on-off controller according to the operating control signal of signal level checker;

Switching power unit adopts the drive signal from the conducting and the on-off controller of closing to drive main switching device and makes it to export desired voltage.

3. switching power unit as claimed in claim 2,

It is characterized in that, the feedback signal of output voltage detector output is transferred to on-off controller by the photodiode of photoelectrical coupler, and the current level of the phototransistor of signal level checker by flowing through photoelectrical coupler is compared with reference current levels and monitored the signal level of feedback signal.

4. switching power unit as claimed in claim 3,

It is characterized in that, the phototransistor of current sensing resistor and photoelectrical coupler is connected in series, and the signal level checker is by picked up signal that the voltage drop on the current sensing resistor is compared with current level verification reference power source, and with this signal as operating control signal feed-in on-off controller, make on-off controller conducting and closing.

5. switching power unit as claimed in claim 2,

It is characterized in that the working power of on-off controller provides with the startup power line, provide from positive power line by starting current that startup resistor provided by starting power line; Or respond in the ancillary coil of the transformer that provides with the steady operation electric current supplying wire and the voltage after the series circuit rectification that a plurality of diodes are formed, the working power of signal level checker is to be provided by the auxiliary control source that is extracted from node between a plurality of diodes.

6. switching power unit as claimed in claim 3,

It is characterized in that, the working power of the phototransistor of signal level checker and photoelectrical coupler is to be provided by the auxiliary control source that is extracted from node between a plurality of diodes, wherein a plurality of diodes are provided by the series circuit that is provided in the steady operation electric current supplying wire, provide the transformer ancillary coil voltages induction and after a plurality of diode rectifications by this supply line.

7. switching power unit as claimed in claim 2,

It is characterized in that, on-off controller can be embodied as control circuit for pulse-width modulation, it exports a pulse signal as the drive signal that drives main switching device, and this pulse signal is the signal after the voltage level of the feedback signal exported according to output voltage detector carries out pulse width modulation.

8. switching power unit as claimed in claim 7,

It is characterized in that, as what control circuit for pulse-width modulation used be-the pulse width modulation controlled integrated circuit, this integrated circuit is realized as integrated circuit (IC) chip, this chip has at least-feedback end and-the soft start capacitor end, the voltage relevant with feedback signal input is input to feedback end, and the voltage that is used to enable or forbid internal circuit is input to the soft start capacitor end.

9. switching power unit as claimed in claim 8,

It is characterized in that, when the pulse width modulation controlled integrated circuit uses as on-off controller,

Also provide the startup adjuster in addition, the startup that is used to proofread and correct the pulse width modulation controlled integrated circuit;

First resistor is connected between the feedback end and negative power line of pulse width modulation controlled integrated circuit;

The signal level checker is according to the assay to the signal level of feedback signal, respectively with operating control signal and inverted feedback signal feed-in soft start capacitor side controller as operation/not operation derailing switch, and feedback end;

The soft start capacitor side controller is connected the soft start capacitor end of pulse width modulation controlled integrated circuit according to operating control signal and disconnects with negative power line; And,

Starting adjuster is connected feedback end by second resistor according to the voltage level of auxiliary control source and disconnects with negative power line.

10. switching power unit as claimed in claim 9 is characterized in that,

The feedback signal of output voltage detector output is transferred to on-off controller by the photodiode of photoelectrical coupler, and the current level of the phototransistor of signal level checker by flowing through photoelectrical coupler is compared with reference current levels and is monitored the signal level of feedback signal

The phototransistor of current sensing resistor and photoelectrical coupler is connected in series, and the signal level checker is by picked up signal that the voltage drop on the current sensing resistor is compared with current level verification reference power source, and with this signal as operating control signal feed-in on-off controller, make on-off controller conducting and closing, and

The signal level checker comprises pair of transistor, the transistorized emitter formation comparator that links together, transistorized base stage is connected to a node between current sensing resistor and the phototransistor, another transistorized base stage is connected to current level verification reference power source, feedback end and another transistorized collector electrode that transistorized collector electrode is connected to the pulse width modulation controlled integrated circuit are connected to the soft start capacitor side controller.

11. switching power unit as claimed in claim 9,

It is characterized in that, the soft start capacitor side controller comprises a NPN transistor, this transistorized collector electrode is connecting the soft start capacitor end of pulse width modulation controlled integrated circuit, emitter is connecting negative power line and base stage is connected to another included in the signal level checker transistorized collector electrode.

12. switching power unit as claimed in claim 9,

It is characterized in that, start adjuster and comprise:

By the series circuit that Zener diode and a plurality of resistor are formed, wherein a plurality of resistors are connected between the line and negative power line of auxiliary control source; And,

NPN transistor, this transistorized base stage is connected to the node between the resistor, and collector electrode is connected to the feedback end of pulse width modulation controlled integrated circuit by second resistor, and emitter is connected to negative power line.

13. switching power unit as claimed in claim 9,

It is characterized in that, the signal level checker comprises: the voltage voltage grading resistor that is used to produce reference voltage, electronegative potential in this voltage grading resistor resistor on one side is divided into two resistors, and its node is each other connecting the soft start capacitor end of pulse width modulation controlled integrated circuit by diode.

14. switching power unit as claimed in claim 9,

It is characterized in that switching power unit also comprises:

Capacitor, it is connected between the soft start capacitor end and negative power line of pulse width modulation controlled integrated circuit;

Diode, it is connected between capacitor and the soft start capacitor end.

15. switching power unit as claimed in claim 8,

It is characterized in that when the pulse width modulation controlled integrated circuit used as on-off controller, switching power unit also comprised:

Current regulator, it is connected between the feedback end and negative power line of pulse width modulation controlled integrated circuit, is used for adjusting according to the signal level of feedback signal the electric current of feedback end output; And,

The soft start capacitor side controller, it is connected with negative power line by the soft start capacitor end with the pulse width modulation controlled integrated circuit according to the output signal of signal level checker and disconnects and be used as operation/not operation derailing switch.

16. switching power unit as claimed in claim 15,

It is characterized in that current regulator comprises a NPN transistor, this transistorized collector electrode is connecting the feedback end of pulse width modulation controlled integrated circuit, and emitter is connecting negative power line by resistor, is being connected the line of feedback signal with base stage.

17. switching power unit as claimed in claim 15,

It is characterized in that, current regulator has comprised a NPN transistor, this transistorized collector electrode is being connected to the feedback end of pulse width modulation controlled integrated circuit, emitter is connecting negative power line by a resistance, base stage is connecting feedback signal line, and what be connected with resistor in series between base stage that is connected described NPN transistor and the negative power line is the NPN transistor that a collector electrode and base stage link together.

18. switching power unit as claimed in claim 8,

Also provide the startup adjuster in addition, to proofread and correct the startup of pulse width modulation controlled integrated circuit;

Also provide the starting switch device in addition, the working power that provides to the signal level checker with opening and closing;

First resistance is connected between the feedback end and negative power line of pulse width modulation controlled integrated circuit;

Signal level checker basis is distinguished soft start capacitor side controller and the feedback end of feed-in as operation/not operation derailing switch to the assay of the signal level of feedback signal with operating control signal and anti-phase feedback signal;

The soft start capacitor side controller is connected the soft start capacitor end of pulse width modulation controlled integrated circuit according to operating control signal and disconnects with negative power line;

Start adjuster and detect whether exist feedback signal, to such an extent as to if the feedback signal of existing starts adjuster and is connected with negative power line by the feedback end of second resistor with the pulse width modulation controlled integrated circuit; If there is no feedback signal starts adjuster and cuts off and being connected of second resistor; And,

Whether the starting switch device detects feedback signal and exists, if to such an extent as to feedback signal of existing, the starting switch device just is provided by the working power that provides to the signal level adjuster, if there is no feedback signal, and the starting switch device then is provided by the working power that provides to the signal level adjuster.

19. switching power unit as claimed in claim 18,

It is characterized in that, the feedback signal of output voltage detector output is transferred to on-off controller by the photodiode of photoelectrical coupler, and the current level of the phototransistor of signal level checker by flowing through photoelectrical coupler is compared with reference current levels and is monitored the signal level of feedback signal, and

The starting switch device comprises a NPN transistor, this transistorized collector electrode is connected to the node between the internal reference voltage line of current sensing resistor that connects feedback signal line and signal level checker, base stage is connecting phototransistor, is being connected negative power line with emitter.

20. switching power unit as claimed in claim 18,

Start adjuster and comprise a NPN transistor, this transistorized collector electrode is connecting the feedback end of pulse width modulation controlled integrated circuit by second resistor, and base stage is connecting phototransistor by a resistor, is being connected negative power line with emitter.

21. switching power unit as claimed in claim 8,

The startup adjuster also is provided in addition, and it is used to proofread and correct the startup of pulse width modulation controlled integrated circuit;

Start adjuster and detect whether exist feedback signal, if to such an extent as to feedback signal of existing, start adjuster and be connected with negative power line with the feedback end of second resistor, and the working power that provides to the signal level checker is provided the pulse width modulation controlled integrated circuit by diode; If there is no feedback signal starts adjuster with regard to being connected of cut-out and diode and second resistor, and the working power that provides to the signal level checker is provided.

22. switching power unit as claimed in claim 21,

It is characterized in that, the feedback signal of output voltage detector output is transferred to on-off controller by the photodiode of photoelectrical coupler, and the current level of the phototransistor of signal level checker by flowing through photoelectrical coupler is compared with reference current levels and is monitored the signal level of feedback signal

Start adjuster and comprise a NPN transistor, this transistorized collector electrode is being connected the feedback end of pulse width modulation controlled integrated circuit by the diode and second resistor, base stage is connecting phototransistor by a resistor, is being connected negative power line with emitter.

23. switching power unit as claimed in claim 21,

It is characterized in that, the signal level checker comprises: the voltage voltage grading resistor that is used to produce reference voltage, electronegative potential in this voltage grading resistor resistor on one side is divided into two resistors, its node is each other connecting the soft start capacitor end of pulse width modulation controlled integrated circuit by diode, and the soft start capacitor side controller is connecting the soft start capacitor end of pulse width modulation controlled integrated circuit by another diode.

24. switching power unit as claimed in claim 8,

The starting switch device also is provided in addition, and it is used for the working power that opening and closing provide to the signal level checker;

Current regulator also is provided in addition, and its connects between the feedback end of pulse width modulation controlled integrated circuit and the negative power line to be used for adjusting according to the signal level of feedback signal the electric current of feedback end output;

The signal level checker according to the assay of the signal level of feedback signal with the soft start capacitor end side controller of operating control signal feed-in as operation/not operation derailing switch;

25. switching power unit with series circuit, it comprises the primary coil of transformer and is connected main switching device between the positive and negative power line, this positive and negative power line is connecting DC power supply again, this switching power unit is carried out switching manipulation by main switching device, induction of high frequency voltage in the secondary coil of transformer, after rectification, obtain direct voltage, with this voltage with originally reference voltage is set and compares, and by controlling main switching device, thereby export needed direct voltage according to the feedback signal that comparative result obtained;

It is characterized in that the signal level of feedback signal is compared with the signal level of the oscillator signal that produces in advance;

According to result relatively, determine the conducting state duty ratio of the drive signal of feed-in main switching device, and carry out in pulse strobe switch control and the switching between the switch control continuously; And,

When in pulse strobe switch control, stopping the switching manipulation of main switching device, stop to be provided for driving the working power of main switching device.

26. switching power unit as claimed in claim 25,

It is characterized in that,, obtain pulse strobe switch control by the working power that opening and closing provide to the on-off controller that drives main switching device.

27. switching power unit as claimed in claim 26,

It is characterized in that, when the pulse width modulation controlled integrated circuit uses as on-off controller, wherein said on-off controller is embodied as the integrated circuit (IC) chip that has feedback end and soft start capacitor end at least, the voltage relevant with feedback signal is input to feedback end, be used to enable and forbid that the voltage of internal circuit is input to the soft start capacitor end, one capacitor is connected between the described feedback end and internal electric source end of pulse width modulation controlled integrated circuit, and wherein the internal electric source end is connecting internal power cord.

28. switching power unit as claimed in claim 26,

It is characterized in that, when the pulse width modulation controlled integrated circuit uses as on-off controller, wherein said on-off controller is embodied as the integrated circuit (IC) chip that has feedback end and soft start capacitor end at least, the voltage relevant with feedback signal is input to feedback end, be used to enable and forbid that the voltage of internal circuit is input to the soft start capacitor end, the series circuit of being made up of capacitor and resistor is connected between the described feedback end and internal electric source end of pulse width modulation controlled integrated circuit, and wherein the internal electric source end is connecting internal power cord.